No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Frequent severe natural disturbances and non-equilibrium landscape dynamics shaped the mountain spruce forest in central Europe
Abstract
Disturbances shape forest structure and composition, but the temporal dynamics of disturbance patterns, their influence on dynamics of forest structural complexity, and the potential impacts of ongoing climate changes are not fully understood. We addressed these issues by focusing on (1) long-term, landscape level retrospective analysis of disturbance dynamics of mountain Norway spruce (Picea abies) forest; (2) testing for the prevailing disturbance agent; and (3) the detection of disturbance drivers, particularly site conditions, using a dendrochronological approach.
... Tropical hurricanes are one of the main factors of natural disturbance, because they severely influence the state, structure, functioning, and composition of ecosystems (Cada et al., 2016;Gill, Jarvis, Veblen, Pickett, & Kulakowski, 2017;Manson & Jardel, 2009), cause species mortality, and generate opportunities for native and invasive species to establish themselves (Cada et al., 2016). Damage caused by tropical hurricanes depends on factors such as proximity, duration, precipitation, wind speed, and biotic and abiotic factors (Doyle, Krauss, & Wells, 2009). ...
... Tropical hurricanes are one of the main factors of natural disturbance, because they severely influence the state, structure, functioning, and composition of ecosystems (Cada et al., 2016;Gill, Jarvis, Veblen, Pickett, & Kulakowski, 2017;Manson & Jardel, 2009), cause species mortality, and generate opportunities for native and invasive species to establish themselves (Cada et al., 2016). Damage caused by tropical hurricanes depends on factors such as proximity, duration, precipitation, wind speed, and biotic and abiotic factors (Doyle, Krauss, & Wells, 2009). ...
... Los ciclones tropicales son uno de los principales factores de disturbios naturales, ya que influyen severamente en el estado, estructura, funcionamiento y composición de los ecosistemas (Cada et al., 2016;Gill, Jarvis, Veblen, Pickett, & Kulakowski, 2017;Manson & Jardel, 2009), causan mortalidad de especies y generan oportunidades de establecimiento para las especies nativas e invasoras (Cada et al., 2016). Los daños ocasionados por los ciclones tropicales dependen de factores como la cercanía, duración, precipitación, velocidad del viento y factores bióticos y abióticos (Doyle, Krauss, & Wells, 2009). ...
Introduction: Tropical hurricanes modify composition and structure of ecosystems. Objective: To analyze the impact of tropical hurricanes on the recovery and resilience of vegetation cover.Materials and methods: The resilience of the lower basin and estuary of San Jose del Cabo was evaluated by studying the impact of 11 tropical hurricanes (2013-2017) on the vegetation cover. Landsat images were analyzed for each event and two SPOT-6 images for the Hurricane Lidia. The areas of gain, stability, loss and recovery of vegetation types were estimated based on the analysis of changes in the Normalized Difference Vegetation Index (NDVI).Results and discussion: Average stability of vegetation cover was 90 %; however, in the case of hurricane Odile (2014) and Lidia (2017), stability decreased considerably, with a loss of 35.4 and 20.5 %, respectively, being the perennial herbaceous vegetation the most affected. One year after Odile and Lidia, recovery was 8.4 % and 25.4 %, respectively; the most recovered vegetation type was reed-tree. The analysis of SPOT-6 images allowed the detailed observation of Lidia's effect on palm grove. The main cause of its loss was runoff from the stream, which favored the growth of invasive species (Arundo donax L. and Tamarix sp.); furthermore, it was estimated that 1.4 ha were deforested, and an area of 20 ha affected by fire in 2017.Conclusion: Vegetation is resilient to tropical hurricanes; however, events that provide more than 50 % of annual precipitation decrease the capacity of vegetation to recover.
... Recent natural disturbances in Central and Eastern European mountain spruce forests have caused extensive mortality across large areas in a few landscapes, while other regions have been subject to more localized smallor moderate-scale events (Senf and Seidl 2018). Likewise, plot-and stand-level dendrochronological reconstructions suggest that mixed-severity disturbance regimes with wide variation of low to high disturbance severities historically operated in mountain spruce forests , Trotsiuk et al. 2014, Cada et al. 2016. The prevailing disturbance agents are windstorms and bark beetle (Ips typhographus) outbreaks ( Cada et al. 2016, Senf andSeidl 2018), although beetle disturbances are often triggered by windthrow events and local weather conditions, particularly droughts. ...
... 2020; Schurman et al. 2018). Data were compiled from published regional studies across a large geographical gradient covering the Carpathian Mountains of southern and northern Romania , Ukraine (Trotsiuk et al. 2014), southern and northern Slovakia (Janda et al. 2017), the Bohemian Forest in the Czech Republic ( Cada et al. 2016), and the Harz Mountains in Germany (Meyer et al. 2017;Fig. 1). ...
... Stands with no evidence of direct human influence, such as logging or livestock grazing, were selected with the help of local experts or primary forest inventories (Mikol a s et al. 2019). In stands of the Bohemian Forest, the prevailing influence of natural disturbances was evident by the significant association of reconstructed events and windstorm and bark beetle (Ips typographus) outbreak events in historical records (see Cada et al. 2016 for more details about possible human influence in these stands). ...
Estimates of historical disturbance patterns are essential to guide forest management aimed at ensuring the sustainability of ecosystem functions and biodiversity. However, quantitative estimates of various disturbance characteristics required in management applications are rare in longer‐term historical studies. Thus, our objectives were to: (1) quantify past disturbance severity, patch size, and stand proportion disturbed, and (2) test for temporal and sub‐regional differences in these characteristics. We developed a comprehensive dendrochronological method to evaluate an approximately two‐century‐long disturbance record in the remaining Central and Eastern European primary mountain spruce forests, where wind and bark beetles are the predominant disturbance agents. We used an unprecedented large‐scale nested design dataset of 541 plots located within 44 stands and 6 sub‐regions. To quantify individual disturbance events, we used tree‐ring proxies, which were aggregated at plot and stand levels by smoothing and detecting peaks in their distributions. The spatial aggregation of disturbance events was used to estimate patch sizes. Data exhibited continuous gradients from low‐ to high‐severity and small‐ to large‐size disturbance events. In addition to the importance of small disturbance events, moderate‐scale (25‐75% of the stand disturbed, >10 ha patch size) and moderate‐severity (25‐75% of canopy disturbed) events were also common. Moderate disturbances represented more than 50% of the total disturbed area and their rotation periods ranged from one to several hundred years, which is within the lifespan of local tree species. Disturbance severities differed among sub‐regions, whereas the stand proportion disturbed varied significantly over time. This indicates partially independent variations among disturbance characteristics. Our quantitative estimates of disturbance severity, patch size, stand proportion disturbed, and associated rotation periods provide rigorous baseline data for future ecological research, decisions within biodiversity conservation, and silviculture intended to maintain native biodiversity and ecosystem functions. These results highlight a need for sufficiently large and adequately connected networks of strict reserves, more complex silvicultural treatments that emulate the natural disturbance spectrum in harvest rotation times, sizes, and intensities, and higher levels of tree and structural legacy retention.
... However, in all types, residual live trees, both dispersed and aggregated in patches, typically persisted post-fire (Berglund and Kuuluvainen 2021). Wind disturbances are also a dominant structuring process across all European forests, though varying greatly in intensity and frequency, for example exhibiting periods when high intensity wind storms are of greater prevalence (Zielonka et al. 2009;Svoboda et al. 2012Svoboda et al. , Čada et al. 2016. Recent research on the role of intermediate severity disturbances suggests a much broader range of variability in the resulting stand age class structure and tree demography than previously recognized for European forests (Nagel et al. 2014, Trotsiuk et al. 2014, Janda et al. 2017. ...
... Forests dominated by Scots pine, of which more than half are in Poland, are predominantly managed by clearcutting systems. Regional studies from the Carpathians, Rila Mountains (Bulgaria), and Bohemia (Czech Republic) suggest that mixed-severity disturbance regimes with wide variation of low to high disturbance severities historically operated in temperate mountain spruce forests (Panayotov et al. 2011, Szewczyk et al. 2011, Trotsiuk et al. 2014, Čada et al. 2016, Janda et al. 2017, Frankovič et al. 2021. We showed that this variability is not emulated by contemporary forest management. ...
In Europe, forest management has controlled forest dynamics to sustain commodity production over multiple centuries. Yet over‐regulation for growth and yield diminishes resilience to environmental stress as well as threatens biodiversity, leading to increasing forest susceptibility to an array of disturbances. These trends have stimulated interest in alternative management systems, including natural dynamics silviculture (NDS). NDS aims to emulate natural disturbance dynamics at stand and landscape scales through silvicultural manipulations of forest structure and landscape patterns. We adapted a “Comparability Index” (CI) to assess convergence/divergence between natural disturbances and forest management effects. We extended the original CI concept based on disturbance size and frequency by adding the residual structure of canopy trees after a disturbance as a third dimension. We populated the model by compiling data on natural disturbance dynamics and management from 13 countries in Europe, covering four major forest types (i.e., spruce, beech, oak, and pine‐dominated forests). We found that natural disturbances are highly variable in size, frequency, and residual structure, but European forest management fails to encompass this complexity. Silviculture in Europe is skewed towards even‐aged systems, used predominately (72.9% of management) across the countries assessed. The residual structure proved crucial in the comparison of natural disturbances and silvicultural systems. CI indicated the highest congruence between uneven‐aged silvicultural systems and key natural disturbance attributes. Even so, uneven‐aged practices emulated only a portion of the complexity associated with natural disturbance effects. The remaining silvicultural systems perform poorly in terms of retention as compared to tree survivorship after natural disturbances. We suggest that NDS can enrich Europe's portfolio of management systems, for example where wood production is not the primary objective. NDS is especially relevant to forests managed for habitat quality, risk reduction, and a variety of ecosystem services. We suggest a holistic approach integrating natural dynamics silviculture with more conventional practices.
... Recurrent hurricanes can create a complex landscape pattern consisting of forest patches of varying ages and sizes at different forest successional stages. In some cases, large wind disturbances may trigger different forest successional pathways and impede a forest landscape from reaching an equilibrium state (Nagel et al. 2014;Čada et al. 2016). ...
... Landscapes in southern and western Changbai Mt. never reached an equilibrium as the proportions of different successional stages were constantly changing. Nonequilibrium for landscapes experiencing infrequent and large disturbances (e.g., hurricanes, wildfires) has been widely reported in other studies (Baker 1989;Nagel et al. 2014;Čada et al. 2016). Notably, the effects of typhoon disturbances on landscape patterns gradually stabilized after 1960, which suggested that with longer timeframe the landscape will continue to shift toward a quasi-equilibrium condition, having less area in recovered patches and more area in recovering patches than those of northern Changbai Mt. ...
Context
Study of interplay of disturbance and forest succession is key to understand forest landscape dynamics, especially under changing climate and disturbance regimes. However, most such studies are from small spatial and temporal scales, and thus may be limited to generalize at large scales.
Objectives
We investigate how typhoons affected forest dynamics at stand and landscape scales, whether the impacts differ among forest biomes, and whether a post-volcanic forest landscape could ultimately reach equilibrium under typhoon disturbances.
Methods
We used landscape modelling to spatially reconstruct the time-series (1710–2010) for the post-volcanic-eruption forest landscapes driven by forest succession and typhoon in Changbai Mountain, China. We compared aboveground biomass (AGB), climax tree species importance value, degree of recovery, and landscape pattern between northern (with typhoons) and southern and western Changbai Mt. (without typhoons).
Results
The effects of typhoon disturbances were minimal when forests were young (before ~1810) but gradually increased as tree grew and forest recovered. The response of forest biomes to typhoon varied, which can be attributed to individual species traits. With recurring typhoons landscape did not reach an equilibrium until 2010. However, the effects of typhoons on landscape pattern gradually stabilized after 1960, suggesting landscapes with typhoons may eventually reach a steady state.
Conclusions
Typhoons have long-lasting and cumulative effects that varied with successional-stages and forest biomes. Landscape under infrequent, large disturbances is nonequilibrium in the short term, but may ultimately reach equilibrium over long time periods. Historical landscape reconstruction reveals fuller spectrum of interplays of typhoons and succession.
... (Pickett & White, 1985). Disturbances, such as windthrow, insect infestation, flooding, or fire, are a significant element of the natural forest dynamic (Čada et al., 2016;Nagel & Diaci, 2006;Nagel et al., 2007), and forestry activities are deemed to be close-to-nature if they are analogous to natural disturbances (Long, 2009;Seymour et al., 2002). With ongoing climate change, disturbance patterns may change, with an increase in disturbance frequency and/or intensity likely in some areas (Seidl et al., 2017). ...
... Wind is the most important natural disturbance agent in Central Europe (Čada et al., 2016;Gardiner et al. 2010), and to date the most researched. In particular, the storms "Vivian and Wiebke" in February 1990 gave rise to intense research effort on windthrow in Switzerland and Germany (Fischer & Fischer, 2009;Nationalparkverwaltung Bayerischer Wald, 2001;Schönenberger et al., 1995;Wohlgemuth & Kramer, 2015). ...
On the basis of long-term surveys of permanent plots and traps, we examined the communities of saproxylic beetles, fungi, herbs, and trees on an untreated 22 ha large beech forest windthrow and asked whether the results lend support to the intermediate disturbance hypothesis (IDH). We studied species richness and the similarity of community composition. Additionally, we grouped species by their frequency trend over time to successional model types to examine whether, corresponding to the IDH, the diversity of these groups explained peak richness at intermediate intervals after the disturbance. In line with the IDH, species richness showed a hump-backed temporal course for alpha and gamma diversity. We found evidence for a linear succession directly after the disturbance. This, however, did not continue, and in all species groups, a partial recovery of the initial community was observed. In the case of fungi, herbs, and trees, but not for saproxylic beetles, alpha diversity was driven by the diversity of the successional model types. Our results underline that the mechanisms driving species richness after disturbances are more complex than the IDH suggests and that these mechanisms vary with species group. We assumed that, besides competition, legacy effects, facilitation, habitat heterogeneity, and random saturation of the species pool are important. In case of trees and herbs, we found indications for strong legacy and competition effects. For fungi and beetles, substrate heterogeneity and microclimate were assumed to be important. We concluded that disturbances contribute to increasing species richness not only by reducing the effectiveness of competitors but also by increasing the amount and diversity of resources, as well as their rate of change over time.
... A study in the Carpathian mountains found a higher disturbance rate in forests established after 1860 compared to "old" forests (Munteanu et al., 2015). These "new" forests may be more susceptible to natural disturbances due to their homogeneous species composition and uniform age structure (Munteanu et al., 2015;Seidl et al., 2011b), as a high disturbance rate in recent years has also been observed in primary and unmanaged spruce stands that developed after major disturbances 19 th century (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). However, a higher disturbance rate in "new" forests could also be the result of different management strategies (e.g., clear ...
... Bebi et al. (2017) analysed the difference in structure between pre-and post-1880 forests in NFI plots across Switzerland, and found that "new" forests do not only have a lower total growing stock, but are also vertically more homogeneous. In unmanaged mountain spruce forests in Central and Eastern Europe, uniform stands established after large disturbance events in the mid-19 th century are now experiencing a new pulse in disturbances (Čada et al., 2016;Janda et al., 2017;Panayotov et al., 2015). In our study, homogeneous spruce stands established only 80-100 years ago are most susceptible to disturbances. ...
... The life cycle dynamics of these forest ecosystems is driven by a specific disturbance regime, which is in some aspects more similar to the dynamics of northern boreal forests than of the temperate mixed and deciduous forests in lower elevations. In old-growth, spruce-dominated mountain forests, stand-replacing disturbances are characteristically caused by abiotic (e.g., windstorm) and biotic (typically an outbreak of spruce bark beetles: Ips typographus L., Ips duplicatus Sahlberg) factors [2,3]. Although fire events cannot be excluded in general, these were common, particularly in early and middle Holocene [4,5]. ...
... Occasional uprooting and breaking of single to several trees or the whole-stand disturbance during storms usually followed by an outbreak of bark beetles can result in canopy openings on scales from small gaps in the size of fractions of a hectare to large areas spanning over thousands of hectares [6][7][8][9]. The disturbance regime of mountain spruce forests shapes their physiognomy, spatial structure, pedocomplexity and even the landform form [10] by enabling re-occurrence of early phases of forest succession and their further development towards the re-establishment of the old-growth forest [3]. ...
Stand-replacing disturbances are a key element of the Norway spruce (Picea abies) forest life cycle. While the effect of a natural disturbance regime on forest physiognomy, spatial structure and pedocomplexity was well described in the literature, its impact on the microbiome, a crucial soil component that mediates nutrient cycling and stand productivity, remains largely unknown. For this purpose, we conducted research on a chronosequence of sites representing the post-disturbance development of a primeval Norway spruce forest in the Calimani Mts., Romania. The sites were selected along a gradient of duration from 16 to 160 years that ranges from ecosystem regeneration phases of recently disturbed open gaps to old-growth forest stands. Based on DNA amplicon sequencing, we followed bacterial and fungal community composition separately in organic, upper mineral and spodic horizons of present Podzol soils. We observed that the canopy opening and subsequent expansion of the grass-dominated understorey increased soil N availability and soil pH, which was reflected in enlarged bacterial abundance and diversity, namely due to the contribution of copiotrophic bacteria that prefer nutrient-richer conditions. The fungal community composition was affected by the disturbance as well but, contrary to our expectations, with no obvious effect on the relative abundance of ectomycorrhizal fungi. Once the mature stand was re-established, the N availability was reduced, the pH gradually decreased and the original old-growth forest microbial community dominated by acidotolerant oligotrophs recovered. The effect of the disturbance and forest regeneration was most evident in organic horizons, while the manifestation of these events was weaker and delayed in deeper soil horizons.
... In deciduous forest understoreys, seasonal canopy phenology causes large changes in light quality and irradiance through the year that potentially produce complex effects on litter decompostion (Pierist e et al., 2019(Pierist e et al., , 2020a. Canopy gap dynamics created by a variety of natural or human disturbances ( Cada et al., 2016), produce heterogeneous light environments in a forest that partially drive species diversity (Wang et al., 2020). This leads to variation in leaf structural and biochemical functional traits (e.g. ...
... Global forests cover about 31% of the land area and their vegetation and soil contain nearly half of the terrestrial biosphere C stock (FAO, 2020), but as nonequilibrium ecosystems they are continuously subject to a variety of disturbances, e.g. wind, landslide or logging ( Cada et al., 2016). Thus, the omission of photodegradation from classical models implies that a considerable proportion of their C loss may have not been identified (Austin & Vivanco, 2006), though identifying the relative importance of photochemical mineralization and photofacilitation requires further research. ...
• Litter decomposition determines carbon (C) backflow to the atmosphere and ecosystem nutrient cycling. Although sunlight provides the indispensable energy for terrestrial biogeochemical processes, the role of photodegradation in decomposition has been relatively neglected in productive mesic ecosystems.
• To quantify the effects of this variation, we conducted a factorial experiment in the understorey of a temperate deciduous forest and an adjacent gap, using spectral-attenuation-filter treatments.
• Exposure to the full spectrum of sunlight increased decay rates by nearly 120% and the effect of blue light contributed 75% of this increase. Scaled-up to the whole forest ecosystem, this translates to 13% loss of leaf-litter C through photodegradation over the year of our study for a scenario of 20% gap. Irrespective of the spectral composition, herbaceous and shrub litter lost mass faster than tree litter, with photodegradation contributing the most to surface litter decomposition in forest canopy gaps. Across species, the initial litter lignin and polyphenolic contents predicted photodegradation by blue light and UV-B radiation, respectively.
• We concluded that photodegradation, modulated by litter quality, is an important driver of decomposition, not just in arid areas, but also in mesic ecosystems such as temperate deciduous forests following gap opening.
... Präventionsmassnahmen gegen Feuer, Windbruch, Lawinenschäden, Insektenbefall und Wildverbiss verhindern oder verringern zudem den Einfluss natürlicher Störungen (Cada et al. 2016;Korpel 1995). Diese sind jedoch wichtige Einflussfaktoren der Walddynamik, sorgen für die Entstehung von Lücken, Freiflächen und lichten Strukturen und damit für eine strukturelle Heterogenität auf Landschaftsebene (Spies und Turner 1999). ...
Die naturnahe Waldwirtschaft schafft zwar vertikal strukturierte Waldbestände, offene Störungsflächen und Strukturen der Alters- und Zerfallsphasen sind jedoch im Vergleich zu Naturwäldern selten. Waldarten, die an solche defizitären Strukturen gebunden sind, sind daher häufig gefährdet. Zur Struktur- und Biodiversitätsförderung im Wald kommen daher unterschiedliche Instrumente zum Einsatz, die gleichzeitig einen Gradienten der forstlichen Nutzungsintensität repräsentieren: von Nicht-Nutzung in grossen Naturwaldreservaten, über die Integration kleiner, unbewirtschafteter Alt- und Totholzinseln in eine bewirtschaftete Waldmatrix, bis hin zur Strukturförderung durch intensive forstliche Eingriffe. Doch welche Artengruppen profitieren wovon? Wie lange dauert es, bis sich die gewünschten Lebensraumstrukturen einstellen? Und kann durch einen kombinierten Einsatz verschiedener, komplementärer Instrumente die Biodiversität auf Landschaftsebene erhöht werden? Im Folgenden werden drei Forschungsprojekte aus Baden-Württemberg vorgestellt, die diese Zusammenhänge beleuchten sollen.
... Importantly, forest resilience to changing disturbance regimes and postdisturbance successional trajectories strongly depends on abiotic or biological legacies, the so-called ecological memory of ecosystems (Swanson et al. 2011, Johnstone et al. 2016. Schurman et al. (2018) determined that disturbance legacies are crucial to the vulnerability of European mountain spruce forests, which are currently being affected by various harmful events resulting in large-scale disturbances across their entire range (Seidl et al. 2014, Schurman 2018, Senf and Seidl 2018, Č ada et al. 2016. Recent dendrochronological research has revealed many new insights into the disturbance history and long-term dynamics of these forests , Zielonka et al. 2010, as well as their patterns of tree regeneration (Diaci et al. 2005, Bače et al. 2015, Wild et al. 2014. ...
... Regional vegetation declined as a response to local climate change feedbacks, persistent drought periods, windthrow damage, and the subsequent impact of the massive spread of, for example, Ips typographus L. (Anderegg et al., 2013;Hlásny et al., 2021a, b). Particularly, predominant Norway spruce stands (Picea abies L. Karst) are prone to beetle outbreaks, due to their high vulnerability to drought periods, rising temperature, and increased storm occurrences under a globally changing climate of the boreal zones (Čada et al., 2016;Macek et al., 2017;Netherer et al., 2021). Extensive and monodominant spruce plantations further amplified the risk of severe outbreaks and large-scale tree mortality during periods of extreme temperature variability (Macek et al., 2017). ...
Europe witnessed a strong increase in
climate variability and enhanced climate-induced
extreme events, such as hot drought periods, mega
heat waves, and persistent flooding and flash floods.
Intensified land degradation, land use, and landcover
changes further amplified the pressure on the environmental
system functionalities and fuelled climate
change feedbacks. On the other hand, global satellite
observations detected a positive spectral greening
trend—most likely as a response to rising atmospheric
CO2
concentrations and global warming. But
which are the engines behind such shifts in surface
reflectance patterns, vegetation response to global
climate changes, or anomalies in the environmental
control mechanisms? This article compares long-term
environmental variables (1948–2021) to recent vegetation
index data (Normalized Difference Vegetation
Index (NDVI), 2001–2021) and presents regional
trends in climate variability and vegetation response
across Europe. Results show that positive trends in
vegetation response, temperature, rainfall, and soil
moisture are accompanied by a strong increase in
climate anomalies over large parts of Europe. Vegetation
dynamics are strongly coupled to increased
temperature and enhanced soil moisture during winter
and the early growing season in the northern latitudes.
Simultaneously, temperature, precipitation, and
soil moisture anomalies are strongly increasing. Such
a strong amplification in climate variability across
Europe further enhances the vulnerability of vegetation
cover during extreme events.
... Regional vegetation declined as a response to local climate change feedbacks, persistent drought periods, windthrow damage, and the subsequent impact of the massive spread of, for example, Ips typographus L. (Anderegg et al., 2013;Hlásny et al., 2021a, b). Particularly, predominant Norway spruce stands (Picea abies L. Karst) are prone to beetle outbreaks, due to their high vulnerability to drought periods, rising temperature, and increased storm occurrences under a globally changing climate of the boreal zones (Čada et al., 2016;Macek et al., 2017;Netherer et al., 2021). Extensive and monodominant spruce plantations further amplified the risk of severe outbreaks and large-scale tree mortality during periods of extreme temperature variability (Macek et al., 2017). ...
Europe witnessed a strong increase in climate variability and enhanced climate-induced extreme events, such as hot drought periods, mega heat waves, and persistent flooding and flash floods. Intensified land degradation, land use, and landcover changes further amplified the pressure on the environmental system functionalities and fuelled climate change feedbacks. On the other hand, global satellite observations detected a positive spectral greening trend—most likely as a response to rising atmospheric CO2 concentrations and global warming. But which are the engines behind such shifts in surface reflectance patterns, vegetation response to global climate changes, or anomalies in the environmental control mechanisms? This article compares long-term environmental variables (1948–2021) to recent vegetation index data (Normalized Difference Vegetation Index (NDVI), 2001–2021) and presents regional trends in climate variability and vegetation response across Europe. Results show that positive trends in vegetation response, temperature, rainfall, and soil moisture are accompanied by a strong increase in climate anomalies over large parts of Europe. Vegetation dynamics are strongly coupled to increased temperature and enhanced soil moisture during winter and the early growing season in the northern latitudes. Simultaneously, temperature, precipitation, and soil moisture anomalies are strongly increasing. Such a strong amplification in climate variability across Europe further enhances the vulnerability of vegetation cover during extreme events.
... In contrast, hurricane winds leave distinct patterns in forest stands in the form of flattened patches or corridors, which modify structure and species composition for several decades or even centuries (e.g. Čada et al. 2016;Kulakowski et al. 2017). Which are the factors that lead to even healthy trees or entire forest areas breaking or being uprooted in strong winds? ...
Depending on wind speed and wind field, storms generate small- to large-scale disturbances, which affect forests more than other ecosystems because of the height and extent of forests. Wind is the most significant disturbance agent for forests. In Europe, western, central, and northern areas have the greatest storm damage in terms of growing stock affected. In Central Europe, coniferous trees – in particular Norway spruce – are more vulnerable to winter storms than broadleaved deciduous trees, which have shed their leaves. Stem breakage and uprooting also depend on factors regarding species identity, site conditions, and stand structure. Another important effect of recurring wind loads – e.g. at forest edges – is that trees adapt by forming compression wood, making them more robust. With respect to regeneration and regrowth after windthrow, trees regrow faster at low than at high elevations. Also, studies have shown that forest regeneration occurs at a similar rate in no-intervention and cleared areas. In the context of climate change, forest disturbance from winter storms is likely to increase.KeywordsClimate changeDeadwoodEconomic damageEuropean winter stormsManagement strategiesNatural regenerationStem breakageTree stabilityWind adaptationWindthrow
... Moreover, compared to other topics frequently discussed in karst hydrology (e.g., karst aquifer recharge, groundwater storage and flow dynamics, contamination problems), the effects of rapid loss of forest cover due to large-scale disturbances on karst hydrology receive less attention in the scientific community (Kovačič et al., 2020). As climate simulations consistently predict more frequent extreme weather events that could lead to forest disturbances (Dale, 2001;Frelich, 2002;Kutnar and Kobler, 2011;Č ada et al., 2016) and as human pressures are increasing, the question arises whether large-scale forest degradation could have an important effect on the recharge of karst aquifer systems. ...
Large-scale forest disturbances (LSFD) are an essential component of forest ecosystem dynamics. The effects of rapid loss of forest cover and other changes in forest ecosystems are inextricably linked to hydrologic processes such as evapotranspiration, soil and recharge processes. Among all hydrogeological systems, karst aquifers are important because of their exceptionally rich and unique biodiversity, biomass, and groundwater resources. At the same time, they are characterized by specific hydrological processes that make them highly vulnerable to environmental changes. Therefore, this study paid special attention to the effects of LSFD on karst hydrology. Using the PRISMA checklist, a thorough literature review of studies published between 2001 and 2020 was compiled into a comprehensive matrix dataset. In addition, an initial assessment of the global and regional distribution of forests on carbonate rocks was made based on publicly available geodatabases of forests and karst aquifers. The compiled information provides the first global overview of hydrological processes affected by LSFD, and identifies important knowledge gaps and future research challenges. The matrix dataset contained 117 full-text articles with a total of 160 case studies. Most publications were from 2011 to 2017, with more than half of the studies at the plot level and more than one-third at the catchment level. Studies on the effects of fires and pest and diseases infestations predominated. However, no articles were found on the effects of ice storms on hydrology in general or on the effects of pest and disease infestations on hydrology in karst areas. Of the 45.6 M km² of forested land worldwide, 6.3 M km² or 13.9% of all forests are underlain by carbonate rocks. Carbonate rocks cover about 15% of the land surface, which means that 31.3% of the world's karst aquifers are covered by forest. 29% of all case studies were conducted in karst areas, which is a high proportion compared to the proportion of forests in karst areas. However, these studies are unevenly distributed geographically. Most studies were conducted at the plot level, and only 21% of studies focused on natural LSFD, so forest management and land use change studies predominated. Although studies on the effects of LSFD on evapotranspiration processes between vegetation, air and soil are fairly well represented, infiltration and recharge processes in karst areas remain poorly understood and knowledge is lacking, particularly on groundwater flow and related hydrological processes. Regional studies and impacts on groundwater resources are also insufficient. The results indicate an urgent need for an integrated holistic interdisciplinary approach and a comprehensive understanding of the individual influencing factors, which would allow more accurate modelling of hydrological processes in forested karst aquifers.
... Over the last decades, due to the global increase in the Earth's temperature, the ecological significance of the spruce bark beetle Ips typographus (L.) infestations have increased in forests including Norway spruce Picea abies (L.) (Fahse & Heurich 2011, Marini et al. 2017, Jakoby et al. 2019, Netherer et al. 2021. Massive outbreaks of this cambiofagous beetle, indigenous in the spruce forests of Europe, constitute a natural phenomenon conditioning the dynamics of these forests (Čada et al. 2016(Čada et al. , Langbehn et al. 2021. As a result, they contribute to the formation of gaps filled in by snags in the forest stand. ...
Tanona M., Czarnota P., 2022. What determines the diversity and succession of lichens inhabiting post-bark beetle snags in the Western Carpathians? Ann. For. Res. 65(1): 65-84. Abstract The life strategy of Norway spruce allows the recovery of European spruce forests in a scenario of catastrophic disturbances caused by the European spruce bark beetle. However, little is known about how the development of this insect infestation has influenced the preservation of the ecological balance in these forests over the last decades. Based on the upper montane spruce forests in the Polish Western Carpathians, we decided to check what species of lichens are using the decaying wood of post-bark beetle snags and how the progressive changes in wood hardness and stand decomposition affect the process of species exchange. In 2018-2019, we investigated spruce snags on permanent monitoring plots in Gorce National Park, whose cause and time of death have been recorded since 1999, and earlier in 1992 and 1997. The study covered 374 post-bark beetle spruce snags at 76 sites. We found 84 species, including 77 lichens, 6 lichenicolous fungi and one non-lichenised fungus, 15 of which were exclusively wood-inhabiting species in Gorce range. Using generalised linear models, the wood age (A) and the scale of the forest stand breakdown phenomenon (B) were compared with the altitude (C), the aspects of hillside exposure (D) and the forest plant community (E) in the assessment of their effect on lichen species diversity and abundance. "A" was the most important of the tested factors, significantly and positively influencing both parameters, while "B-D" only weakly influenced lichen abundance. Five groups of wood age, significantly different in the lichen abundance and the composition of species were distinguished, and a characteristic combination of dominant species was determined for each of them. Based on the measurements of the wood hardness under the thalli using Shore's method, the succession of species during the colonisation of the post-bark beetle snags was determined and four groups of species were selected, most frequent in the successive stages of wood decay process. The wood of spruces killed by the bark beetle is both an important substrate enabling the survival of obligately wood-inhabiting lichen species, as well as providing a habitat supporting the maintenance of epiphytes in the Carpathian forests. This study extends the knowledge about the specific requirements of lichens inhabiting spruce snags, as well as the pace and course of lichen succession on this substrate.
... As a rule, intensive logging has adverse consequences for saproxylic beetle biodiversity when removing wood after a disturbance 7 . The natural development of forests results in the gradual disturbance of homogeneous structures, usually by wind 27,28 , but also by insect outbreaks and fire 29 . Forests were also shaped by large herbivores in the past 30,31 . ...
Natural dynamics in forests play an important role in the lives of many species. In the landscape of managed forests, natural disturbances are reduced by management activities. This usually has a significant effect on insect diversity. The effect of small-scale natural dynamics of protected beech stands on the richness of saproxylic and non-saproxylic beetles was investigated. Sampling was carried out by using flight interception traps in the framework of comparing different developmental stages: optimum, disintegration, and growing up, each utilizing 10 samples. We recorded 290 species in total, of which 61% were saproxylic. The results showed that the highest species richness and thus abundance was in the disintegration stage. In each developmental stage, species variation was explained differently depending on the variable. Deadwood, microhabitats, and canopy openness were the main attributes in the later stages of development for saproxylic beetles. For non-saproxylics, variability was mostly explained by plant cover and canopy openness. Small-scale disturbances, undiminished by management activities, are an important element for biodiversity. They create more structurally diverse stands with a high supply of feeding and living habitats. In forestry practice, these conclusions can be imitated to the creation of small-scale silvicultural systems with active creation or retention of high stumps or lying logs.
... Importantly, forest resilience to changing disturbance regimes and postdisturbance successional trajectories strongly depends on abiotic or biological legacies, the so-called ecological memory of ecosystems (Swanson et al. 2011, Johnstone et al. 2016. Schurman et al. (2018) determined that disturbance legacies are crucial to the vulnerability of European mountain spruce forests, which are currently being affected by various harmful events resulting in large-scale disturbances across their entire range (Seidl et al. 2014, Schurman 2018, Senf and Seidl 2018, Č ada et al. 2016. Recent dendrochronological research has revealed many new insights into the disturbance history and long-term dynamics of these forests , Zielonka et al. 2010, as well as their patterns of tree regeneration (Diaci et al. 2005, Bače et al. 2015, Wild et al. 2014. ...
Development of primary spruce forests is driven by a series of disturbances, which also have an important influence on the understorey vegetation and its diversity. Early post-disturbance processes have been intensively studied, however, very little is known about the long-term effects of disturbances on the understorey. We quantified disturbance history using dendrochronological methods to investigate its impact on vascular plant diversity and understorey species composition. We sampled 141 plots randomly assigned throughout primary stands located in the zone of natural montane acidophilous forests dominated by Picea abies (L.) Karst. in the Western Carpathians. Dendrochronological, dendrometric, and environmental parameters were related to understorey properties using ordination methods and a Bayesian approach using multilevel linear models (GLMM).
Time since the last disturbance (23–260 years ago; mostly windstorms and bark beetle outbreaks) had a significant effect on understorey species composition of the current communities, and it also interacted with disturbance severity to influence species diversity. The effect of disturbances on the understorey was largely mediated by the alteration of stand structure (age, DBH, canopy openness), Vaccinium myrtillus L. cover, and topsoil chemical properties. A period of severe disturbances between 1860 and 1890 resulted in a legacy of our current, relatively homogeneous spruce stands with less diverse sciophilous understorey dominated by V. myrtillus, which is in contrast to heterogeneous stands (in terms of age and spatial structure) driven by small-scale, lower-severity disturbances, which led to an understorey enriched by species with higher demands on light and topsoil quality (higher K concentration and lower C/N ratio).
All developmental pathways following disturbances create a unique complex of spatiotemporal understorey variability in the montane spruce forests. Therefore, to preserve their full diversity, disturbances of all severities and sizes should be accepted as natural drivers, both in the field of nature conservation and close-to-nature forestry efforts.
... A substantial proportion of the extant Bohemian forest developed following a period of high natural disturbance activity in the early 1800s. Most stands are considered to be relatively unmodified by anthropogenic land use, as logging rates were limited in the 19th century and increasingly curtailed by conservation measures in the 20th century (Brůna et al., 2013;Č ada et al., 2016;Svoboda et al., 2012). A majority of the region is now protected by two reserves, the Bavarian Forest National Park in Germany and Š umava National Park in Czechia. ...
Plant traits are an expression of strategic tradeoffs in plant performance that determine variation in allocation of finite resources to alternate physiological functions. Climate factors interact with plant traits to mediate tree survival. This study investigated survival dynamics in Norway spruce (Picea abies) in relation to tree-level morphological traits during a prolonged multi-year outbreak of the bark beetle, Ips typographus, in Central Europe. We acquired datasets describing the trait attributes of individual spruce using remote sensing and field surveys. We used nonlinear regression in a hypothesis-driven framework to quantify survival probability as a function of tree size, crown morphology, intraspecific competition and a growing season water balance. Extant spruce trees that persisted through the outbreak were spatially clustered, suggesting that survival was a non-random process. Larger diameter trees were more susceptible to bark beetles, reflecting either life history tradeoffs or a dynamic interaction between defense capacity and insect aggregation behavior. Competition had a strong negative effect on survival, presumably through resource limitation. Trees with more extensive crowns were buffered against bark beetles, ostensibly by a more robust photosynthetic capability and greater carbon reserves. The outbreak spanned a warming trend and conditions of anomalous aridity. Sustained water limitation during this period amplified the consequences of other factors, rendering even smaller trees vulnerable to colonization by insects. Our results are in agreement with prior research indicating that climate change has the potential to intensify bark beetle activity. However, forest outcomes will depend on complex cross-scale interactions between global climate trends and tree-level trait factors, as well as feedback effects associated with landscape patterns of stand structural diversity.
... Practical approaches in the field also differ, with some NBFM proponents only advocating selection management, while most NBFM advocates and practitioners employ a variety of silvicultural tools, including clearcutting in rare cases, and focus on tailoring interventions to site ecology, stand conditions and management objectives (Schütz 1990;Fries et al. 1998;Boncina 2011b (Nagel et al. 2013a;Čada et al. 2016). Research suggests that nature-based silvicultural systems are consistent with historical disturbance regimes of forest ecosystems (Nagel et al. 2014), while mimicking stand replacing disturbances in other sites is constrained by forest health or direct protective functions of the forest. ...
What is Closer to Nature Forest Management?
Closer-to-Nature Forest Management is a new concept proposed in the EU Forest Strategy for 2030, which aims to improve the conservation values and climate resilience of multifunctional, managed forests in Europe. Building on the latest scientific evidence, this report attempts to define the concept based on a set of seven guiding principles. It also outlines a framework/checklist for flexible European-wide implementationof the concept.
The 7 principles of Closer-to-Nature Forest Management are:
1. Retention of habitat trees, special habitats, and dead wood
2. Promoting native tree species as well as site adapted non-native species
3. Promoting natural tree regeneration
4. Partial harvests and promotion of stand structural heterogeneity
5. Promoting tree species mixtures and genetic diversity
6. Avoidance of intensive management operations
7. Supporting landscape heterogeneity and functioning
This report analyses the current pressures on forest biodiversity as well as on the health of, and resilience in, managed forests. It examines existing nature-oriented forest management approaches in Europe and analyses their ability to support biodiversity, their stability and adaptability to uncertain future conditions. It proposes a definition, a set of guiding principles and a framework for flexible European-wide implementation of Closer-to-Nature Forest Management. Finally, it evaluates barriers and enablers for implementation and presents a list of existing networks that can be used to assist the dissemination of Closer-to-Nature Forest Management throughout Europe.
How can we implement this new concept?
1. Different regions need different management approaches: While the general principles of Closer-to- Nature Forest Management should be similar across all regions, varying but related management approaches should be used in different regions of Europe. This reflects the variation in forest types across the continent,
differences in the intensity and scale of natural disturbance regimes, and the ways forests have been used in the past and will have to be managed in the future.
2. Learn from the past and consolidate existing networks and demonstrations: There is a long European tradition of nature-based forest management concepts, and there are many opportunities to learn from existing practices. Because the wider adoption of Closer-to-Nature Forest Management will require a substantial effort in knowledge transfer, it is very important to consolidate existing networks of trials and demonstrations. Such a knowledge transfer network should cover all major regions and forest types found in
Europe and could be linked to others seeking to preserve traditional and sustainable management methods, cultural landscapes and their associated biocultural diversity. This will be invaluable in the ongoing social learning process and in helping to convince forest managers and other stakeholders of the benefits of this approach.
3. Use adaptive management as a way to tackle uncertainties: We need to regularly monitor forest responses to management interventions, evaluate these responses and adjust management strategies accordingly. A similar adaptive approach is urgently required to evaluate the impact of policy measures and support
mechanisms proposed to encourage adoption of Closer-to-Nature Forest Management.
4. Not a quick-fix, long-term measures are needed: The introduction of Closer-to-Nature Forest Management is not a ‘quick-fix’ and policy makers must provide long-term and consistent support measures to encourage forest managers and other stakeholders to adopt this strategy. Support for forest owners for training and application of the strategy is key.
5. Review existing subsidy and taxation regimes for private owners: Convincing private owners to follow this approach will require the creation of schemes that reward them for providing ecosystem services. Closer-to- Nature Forest Management has the potential to support biodiversity, adapt forests to climate change and provide ecosystem services to a higher level than conventional forest management. There is an urgent need to review existing subsidy and taxation regimes affecting private forestry, and to consider how these might be changed to further the uptake of Closer-to-Nature Forest Management.
6. Develop and use new technologies and tools: There is a need to harmonize monitoring systems and to develop and use new technologies and tools (GIS, GPS and remote sensing) to ease management of these more diverse and structure-rich forests.
Finally, there are still some uncertainties about the effect of certain elements of Closer-to-Nature Forest Management on biodiversity conservation and ecosystem health, and how they will affect other ecosystem services including wood production under different management conditions throughout Europe. This calls for more collective learning, experimentation and research.
... Regional vegetation declined as a response to local climate change feedbacks, persistent drought periods, windthrow damage, and the subsequent impact of the massive spread of, for example, Ips typographus L. (Anderegg et al., 2013;Hlásny et al., 2021a, b). Particularly, predominant Norway spruce stands (Picea abies L. Karst) are prone to beetle outbreaks, due to their high vulnerability to drought periods, rising temperature, and increased storm occurrences under a globally changing climate of the boreal zones (Čada et al., 2016;Macek et al., 2017;Netherer et al., 2021). Extensive and monodominant spruce plantations further amplified the risk of severe outbreaks and large-scale tree mortality during periods of extreme temperature variability (Macek et al., 2017). ...
Europe witnessed a strong increase in climate variability and enhanced climate-induced extreme events, such as hot drought periods, mega heat waves, and persistent flooding and flash floods. Intensified land degradation, land use, and landcover changes further amplified the pressure on the environmental system functionalities and fuelled climate change feedbacks. On the other hand, global satellite observations detected a positive spectral greening trend—most likely as a response to rising atmospheric CO2 concentrations and global warming. But which are the engines behind such shifts in surface reflectance patterns, vegetation response to global climate changes, or anomalies in the environmental control mechanisms? This article compares long-term environmental variables (1948–2021) to recent vegetation index data (Normalized Difference Vegetation Index (NDVI), 2001–2021) and presents regional trends in climate variability and vegetation response across Europe. Results show that positive trends in vegetation response, temperature, rainfall, and soil moisture are accompanied by a strong increase in climate anomalies over large parts of Europe. Vegetation dynamics are strongly coupled to increased
temperature and enhanced soil moisture during winter and the early growing season in the northern latitudes. Simultaneously, temperature, precipitation, and soil moisture anomalies are strongly increasing. Such a strong amplification in climate variability across Europe further enhances the vulnerability of vegetation cover during extreme events.
... Disturbances caused by natural factors have occurred in the past and cannot be avoided in the future. In the years 1950-2000, the annual average timber volume damaged by disturbances was 35 million m 3 [14][15][16]. ...
The area of forests and the standing volume per hectare are constantly increasing in Eu-rope, and this trend is expected to continue for several more decades; the aim of this paper was to provide an empirical overview of the development of disturbances in selected countries of central Europe and based on this overview to empirically model and predict the development and intensity of disturbances in the future. Statistical methods (Holt-Winters) and predictive risk models of the growth simulator SIBYLA were used for prediction. From the statistically predicted values by this method, it follows that, in the next three years, it is possible to assume that stagnation will result in declining volumes of incidental fellings in all countries. Forecast from the growth simulator SIBYLA shows a substantial increase in the predicted volume of incidental fellings for the years 2021 and 2022, compared with 2020. The volumes of incidental fellings should grow most significantly, especially in Germany, Poland, and Austria. The performed analysis and predictions suggest that the peak of wood volumes damaged by disturbances in the next decade will probably be reached already in the reports for 2021 or 2022. However, the risk of disturbances remains high, and other large-scale area disturbances in forest ecosystems cannot be completely ruled out.
... More large, high severity disturbances may cause a homogenization of forests, amplifying future climate impacts and potentially leading to forest loss . Increases in the frequency of low to moderate severity disturbances (e.g., small-scale windthrow, or insect outbreaks in mixed forests), however, may enhance structural and compositional complexity (Čada et al., 2016;Halpin & Lorimer, 2016) and dampen the effect of future climate-mediated disturbances (Sommerfeld et al., 2021). More broadly, a development towards structurally and functionally complex forests (e.g., found in old-growth forests) is expected to buffer the effects of climate change compared with younger and/ or less complex forests (Bauhus et al., 2009;. ...
Observational evidence suggests that forests in the Northern Alps are changing at an increasing rate as a consequence of climate change. Yet, it remains unclear whether the acceleration of forest change will continue in the future, or whether downregulating feedbacks will eventually decouple forest dynamics from climate change. Here we studied future forest dynamics at Berchtesgaden National Park, Germany by means of a process‐based forest landscape model, simulating an ensemble of 22 climate projections until the end of the 21st century. Our objectives were (i) to assess whether the observed acceleration of forest dynamics will continue in the future, (ii) to analyze how uncertainty in future climate translates to variation in future forest disturbance, structure, and composition, and (iii) to determine the main drivers of future forest dynamics. We found that forest dynamics continue to accelerate in the coming decades, with a trend towards denser, structurally more complex and more species rich forests. However, changes in forest structure leveled off in the second half of the 21st century regardless of climate scenario. In contrast, climate scenarios caused trajectories of tree species change to diverge in the second half of the 21st century, with stabilization under RCP 2.6 and RCP 4.5 scenarios and accelerated loss of conifers under RCP 8.5. Disturbance projections were 3 to 20 times more variable than future climate, whereas projected future forest structure and composition varied considerably less than climate. Indirect effects of climate change via alterations of the disturbance regime had a stronger impact on future forest dynamics than direct effects. Our findings suggest that dampening feedbacks within forest dynamics will decelerate forest change in the second half of the 21st century. However, warming beyond the levels projected under RCP 4.5 might profoundly alter future forest disturbance and composition, challenging conservation efforts and ecosystem service supply.
... Furthermore, natural or human disturbances including wind, tree mortality and harvesting, create heterogeneity in forest structure (e.g. gaps) (Nakashizuka and Matsumoto, 2002;Čada et al., 2016), which further modify the characteristics of understorey solar irradiance. Solar irradiance modulates litter decomposition processes through photodegradation, which mainly consists of direct photomineralization and indirect photofacilitation (Gallo et al., 2009;King et al., 2012;Almagro et al., 2015;Liu et al., 2018). ...
Decomposition of plant organic matter plays a key role in the terrestrial biogeochemical cycles. Sunlight has recently been identified as an important contributor to carbon [C] turnover through photodegradation, accelerating decomposition even in forest ecosystems where understorey solar irradiance remains relatively low. However, it is uncertain how C and nutrients dynamics respond to fluctuations in solar spectral irradiance caused by canopy structure (understorey vs. gaps) and season (open vs. closed canopy phenology). Spectral-attenuation treatments were used to compare litter decomposition over eight months, covering canopy phenology, in a temperate deciduous forest and an adjacent gap. Exposure to the full spectrum of sunlight increased the loss of litter C and lignin by 75% and 64% in the forest gap, and blue light was responsible for respectively 27% and 42% of that loss. Whereas in the understorey, C and lignin loss were similar among spectral-attenuation treatments over the experimental period, except prior to and during spring canopy flush when exposure to the full spectrum of sunlight promoted C loss by 15% overall, 80% of which was attributable to ultraviolet-B (UV-B) radiation. Nitrogen [N] was immobilized in the understorey during canopy flush before the canopy completely closed but N was swiftly released during canopy leaf-fall. Our study suggests that blue-driven photodegradation plays an important role in lignin decomposition and N dynamics in canopy gaps, whereas seasonal canopy phenology affecting sunlight reaching the forest floor drastically changes patterns of C and N in litter during decomposition. Hence, including sunlight dynamics driven by canopy structure and phenology would improve estimates of biogeochemical cycling in forests responding to changes in climate and land-use.
... Natural disturbances are widely acknowledged to be a primary force in the dynamics of diverse primeval forest ecosystems, shaping the forest structure and composition and maintaining species and soil diversity [1][2][3][4][5][6]. Whereas fine-scale disturbances dominate the natural forest dynamics of deciduous upland forests of Central Europe [7][8][9][10], several studies have highlighted the importance of large-scale, stand-replacing events for conifer mountain forest ecosystems [11][12][13][14][15]. More recently, a mixed-severity disturbance regime, predominantly driven by gap dynamics with infrequent severe stand-replacing events, has been documented for some mixed mountain forest ecosystems [8,13,[16][17][18][19][20]. ...
The driving forces of tree mortality following wind disturbances of mountain mixed European temperate forests belongs among issues not comprehensively resolved. Hence, we aimed to elucidate the key factors of tree resistance to historical severe disturbance events in the Boubínský Primeval Forest, one of the oldest forest reserves in the Czech Republic. By using spatially explicit tree census, dendrochronological and soil data, we study spatial and temporal patterns of past disturbances and mathematically compared selected characteristics of neighboring trees that were killed by a severe storm in 2017 and those that remained undisturbed. The tendency of trees toward falling was primarily driven edaphically, limiting severe events non-randomly to previously disturbed sites occupied by hydromorphic soils and promoting the existence of two spatially-separated disturbance regimes. While disturbed trees usually recruited in gaps and experienced only one severe release event, surviving trees characteristically regenerated under the canopy and were repeatedly released. Despite the fact that disturbed trees tended to reach both lower ages and dimensions than survivors, they experienced significantly higher growth rates. Our study indicates that slow growth with several suppression periods emerged as the most effective tree strategy for withstanding severe windstorms, dying of senescence in overaged life stage. Despite the selective impact of the Herwart storm on conifer population, we did not find any difference in species sensitivity for most characteristics studied. We conclude that the presence of such ancient, high-density wood trees contributes significantly to the resistance of an entire stand to severe storms.
... Forests that exhibit reverse J-shaped distributions are more structurally complex by having a diversity of tree size and age classes yet such a distribution might not be within the range of natural dynamics of primary spruce forests because they have been historically shaped by mixed-severity disturbances (e.g. Č ada et al., 2016;Meigs et al., 2017). ...
Natural disturbances strongly influence forest structural dynamics, and subsequently stand structural heterogeneity, biomass, and forest functioning. The impact of disturbance legacies on current forest structure can greatly influence how we interpret drivers of forest dynamics. However, without clear insight into forest history, many studies default to coarse assumptions about forest structure, for example, whether forests are even or unevenly aged. The aim of this study was to analyze the effects of past disturbances on the current diameter distributions of Norway spruce (Picea abies (L.) Karst.)-dominated landscapes throughout the Carpathian Mountains. Our dendroecological dataset comprises tree cores from 339 plots (7,845 total tree cores), nested within 28 primary forest stands, known to vary greatly in the severity of historical disturbances. Our analyses revealed that historical disturbances had a strong and significant effect on the current diameter distribution shapes at the plot level. We demonstrated that mixed-severity disturbance regimes were more frequent and create a complex pattern of diameter distributions at the plot and stand scale. Here, we show that high severity disturbance was associated with unimodal diameter distributions, while low and moderate severity was associated with the reverse J-shaped distribution. This is a result of complex disturbance patterns, with structural biological legacies. Our results will have important management implication in the context of tree size heterogeneity, biomass storage, and productivity as influenced by natural disturbances. Lastly, these results demonstrate that structural changes may arise as consequences of changing disturbance regime associated with global change.
... In the Tatras, similar calamities of a smaller extent occurred, for example, in the early 20th century. Those areas influenced by stand replacing disturbances will be resistant to further disturbances for several decades, because of the more resilient forest structure (bark beetle usually attacks trees older than 60 years, when considering natural conditions) [5,6]. However, more frequent bark beetle outbreaks are expected in the future, as a consequence of climate change [41]. ...
High winds and the subsequent infestation of subcortical insect are considered to be the most extensive types of large natural disturbances in the Central European forests. In this paper, we focus on the landscape dynamics of two representative mountain areas of Slovakia, which have been affected by aforementioned natural disturbances during last two decades. For example, on 19 November 2004, the bora caused significant damage to more than 126 km2 of spruce forests in the Tatra National Park (TANAP). Several wind-related events also affected sites in the National Park Low Tatras (NAPALT). Monitoring of related land cover changes during years 2000–2019 was based on CORINE Land Cover data and methodology set up on satellite and aerial images interpretation, on detailed land cover interpretation (1:10,000) for the local case studies, as well as on the results of field research and forestry databases. The dynamics of forest recovery are different in the clear-cuts (usually with subsequent tree planting) and in the naturally developing forest. The area in the vicinity of Tatranská Lonmnica encroaching on the Studená dolina National Nature Reserve in TANAP represents a trend of the gradual return of young forest. The area of Čertovica on the border between NAPALT and its buffer zone are characterized by an increase in clear-cut sites with potentially increasing soil erosion risk, due to repeated wind disasters and widening of bark beetle. Proposed detailed, large-scale approach is being barely used, when considering recent studies dealing with the natural disturbances.
... We simulated three disturbance scenarios: historic disturbance, future disturbance and no disturbance. The three scenarios differed in disturbance frequency, as determined by the disturbance rotation period (i.e. the average time it takes for the cumulative area of disturbance to reach the size of the study landscape), which was set to 400 years in the historic disturbance scenario (Čada et al., 2016;Thom et al., 2013), and to 200 years in the future disturbance scenario . This implies that in the future disturbance scenario twice as many disturbance events occurred compared to the historic disturbance scenario, which is within the range of expec- In total, 5,040 simulation runs with a duration of 200 years were conducted (2 models × 2 landscapes × [3 levels of gamma diversity × 2 spatial configurations +1 × no diversity] × 3 climate scenarios × 3 disturbance scenarios × 20 replicates). ...
Single species forest systems often suffer from low resistance and resilience to perturbations. Consequently, fostering tree species diversity is discussed as an important management approach to address the impacts of changing climate and disturbance regimes. Yet, the effect of the spatial grain of tree species mixtures remains unknown.
We asked whether increasing tree species diversity between stands (beta diversity) has the same effect as increasing tree species diversity within stands (alpha diversity) at similar overall levels of richness (gamma diversity). We conducted a multi‐model simulation experiment under climate change, applying two forest landscape models (iLand and LandClim) across two contrasting landscapes of Central Europe. We analysed the effect of different levels and configurations of diversity on the disturbance impact and the temporal stability of biomass stocks and forest structure.
In general, increasing levels of diversity decreased disturbance impacts. Positive diversity effects increased with increasing severity of climate change. Beta diversity buffered disturbance impacts on landscape‐level biomass stocks more strongly than alpha diversity. The effects of the spatial configuration on forest structure were more variable. Diversity effects on temporal stability were less pronounced compared to disturbance impacts, and mixture within and between stands had comparable effects on temporal stability.
Diversity effects were context‐dependent, with patterns varying between landscapes and indicators. Furthermore, we found a strong species identity effect, with increasing diversity being particularly beneficial in conifer‐dominated systems of the European Alps. The two models agreed on the effects of different levels and configurations of tree species diversity, underlining the robustness of our findings.
Synthesis and application . Enhancing tree species diversity can buffer forest ecosystems against increasing levels of perturbation. Mixing tree species between stands is at least as effective as mixing tree species within stands. Given the managerial advantages of between‐stand mixtures (e.g. reduced need to control competition to maintain diversity, higher timber quality, lower logistic effort), we conclude that forest management should consider enhancing diversity at multiple spatial scales.
... Discrete weather events, such as storms or heatwaves, are important drivers of disturbances in marine systems, where they are expected to increase in frequency and severity under most future climate change scenarios (IPCC 2014, Cai et al. 2015, Oliver et al. 2019. The response of communities and ecosystems to disturbances de -pends on characteristics of the events, such as the type, frequency, intensity and extent of disturbance (McCabe & Gotelli 2000, Sousa 2001, Benedetti-Cecchi et al. 2006, Vaselli et al. 2008, Thakur et al. 2014, Čada et al. 2016. At the same time, disturbance effects can also vary dramatically according to characteristics independent of the events, such as the specific local biotic and abiotic context (Dudgeon & Petraitis 2001, Wernberg & Connell 2008, Kramer et al. 2014. ...
Disturbances often control community structure by removing large dominant species,
allowing new species to colonize. Disturbances vary in intensity and extent, and their effects on resident communities can depend on local environmental conditions. We tested the effects of disturbance intensity and extent on different functional groups of understory species in kelp forests at 4 locations along an ocean climate gradient in Western Australia. We hypothesized that, compared to intact canopies, increasing disturbance intensities (50 and 100% of kelp removal) and extents (2, 4 and 8 m diameter) would promote light-dependent competitors (turf, foliose, articulated coralline and fucoid seaweeds) at the expense of less light-dependent functional groups (invertebrates and encrusting seaweeds). We also hypothesized that these effects would be most pronounced at warmer relative to cooler locations, where metabolic and ecological rates
are faster. The first hypothesis was supported; light-dependent understory groups (turfs, in particular) increased, while less light-dependent groups (crusts in particular) decreased with increasing disturbance regimes. However, the second hypothesis was not supported; even though understory communities differed between locations and turf covers were highest at the warmest location, we found no significant interactions between locations and disturbance regimes. Importantly, our results revealed that even small-scale partial canopy loss can have significant effects on kelpassociated communities. The implied community-wide, density-dependent effects have implications for the management and conservation of kelp forests, because restoration of ecological functions must also consider the density of kelp forests, not simply their presence or absence.
... Spruce stands have been dying out since the end of the 1950s. The dying-off process in mountain spruce forests was caused by several biotic (bark beetles) and non-biotic factors (air pollution), forming a cause-and-effect chain that reinforced the disease process, resulting in a total annihilation of the stand over an extended period of time [81][82][83]. Air pollution, prolonged summer droughts in the years 2003-04 and 2006-07, and the catastrophic hurricane of 2004 resulted in the weakening of spruce stands in the montane zone [84,85]. ...
Changes in forest range are caused by human activity in many regions of the world.
The aim of this paper is an attempt to determine the impact of pastoral and forest management on
changes in forest cover and their fragmentation in the Silesian Beskids (southern Poland) in 1848–2015.
Historical maps and landscape metrics were used to study changes in forest cover. Using a digital
map of forests, analyses of the distribution of forest communities, site types and their condition were
conducted. Since 1848 the forest area has increased by 11.8%, while the area of forest core zones has
increased by 16.2%, accompanied by a 4.5% reduction in the forest’s internal bu�er zone. From the
mid-nineteenth century, the forest range has been systematically growing from 82.1 to 93.9% because
of the pastureland abandonment and forest regeneration, despite temporary logging resulting in
forest fragmentation. Minor changes in core area index (CAI) from 80.41 to 87.55 indicate that pastoral
economy did not result in considerable fragmentation of forests. The impact of forest management
was greater as the sites characterised by natural condition occupy only 28% of the forest land and
anthropogenically transformed ones dominate occupying over 50%. An artificial spruce monoculture
was died-o� and large felling areas were created at the beginning of the twenty-first century covering
almost 40% of the study area.
... Disturbance chronologies have usually been truncated when the sample size drops below 10 (Butler and Sawyer, 2008;Fraver et al., 2009). However, even a lower sample size (7) showed reliable results at the community level (Cada et al., 2016). Samonil et al. (2015) identified the level of uncertainty for such low sample size and suggested following solutions: 1) increase sample size, 2) truncate the starting year of disturbance chronology and/or 3) broadening the merging intervals of disturbance chronology. ...
Disturbances play an important role in forest dynamics. The determination of long-term spatiotemporal characteristics of disturbance regimes is essential for understanding forest dynamics and its shifts under global changes. Tree rings are known to provide detailed insight into both temporal and spatial patterns of forest disturbance history. One of the most commonly used indirect tree-ring techniques for investigating past disturbances is growth release detection (GRD), i.e. the abrupt radial growth increase of trees as a reaction to improved light conditions after the death of a disturbed neighbouring canopy tree or trees. However, there are several issues which have not been addressed so far. Here, an overview of GRD and guide for researchers aiming to incorporate GRD into their research is provided, with focus on conventional running mean methods. The aim is to cover various issues of the GRD procedure such as sampling strategy and data quality, selection of appropriate methods and parameter settings, suggested analysis procedures as well as result presentation. Overall, the importance of GRD incorporation in multidisciplinary studies of forest dynamics is highlighted, as it offers a precise tool for gathering long-term information about past disturbances. Lastly, this paper also suggests several future challenges focused on possible utilization of GRD in mainstream ecology to answer long-standing global ecological questions and improve understanding of past processes in forest ecosystems.
Analysis of long-time climate data since 1961 from the selected meteorological station Churáňov was connected with state of Norway spruce forests in the area of spruce natural occurrence and their main pest species, Ips typographus, in the Šumava Mts. The current climate change was described using set of variables based on air temperature, relative air humidity and precipitations. Data were used for calculation specific indices, which are related to dynamics of Picea abies (growth index) and spruce bark beetle (date of first infestation and achieved bark beetle development [G], have been calculated by the PHENIPS model). Average air temperature increase was +0.37 °C per 10 years. Slight air humidity decrease shows a discontinuity between 1994 and 1995. Total volume of precipitation is rather constant. Increase of temperatures results in earlier onset of both vegetation growth and I. typographus first infestation (average shift of 1.5 days per 10 years). The modelled bark beetle's first infestation corresponds to numbers of individuals caught in the pheromone traps. The number of generations and the achieved development state of I. typographus was stable until 1991, from 1992 there was an increase, which was followed by past growing trend. The results from the Churáňov in mountain region of natural Norway spruce forests are compared with ones from whole area of the Czech Republic, where planted P. abies forests prevails.
Bark beetle disturbances are a critical event in the life cycle of Norway spruce forests. However, our knowledge of their effects on ectomycorrhizal fungi (EMF), which play a key role in forest productivity and nutrient cycling, is still incomplete. Special attention has been paid to the dynamics and diversity of EMF communities in managed forests, but studies dealing with disturbed natural stands are underrepresented. We conducted a study in an unmanaged natural spruce forest in the Bohemian Forest, (Czech Republic) which suffered severe forest dieback caused by bark beetle. Approximately a decade after the disturbance, the character of the forest structure in the study area (∼60 ha, 41 study plots) ranged from sites with open canopy and sparse tree cover to areas with dense spruce regeneration to patches of closed-canopy forest. We found that relative EMF abundance in soils was positively related to surviving tree and regeneration density. The number of surviving trees also positively affected species EMF richness and tended to support preservation of late-successional EMF species. Our results suggest that trees that survive bark beetle disturbance are key for the fate of the EMF community in natural forests.
Natural disturbances and subsequent outbreaks of forest insects led to unprecedented amounts of damaged timber. In Eurasia, the European Spruce Bark Beetle ( Ips typographus ) breeding in Norway spruce ( Picea abies ) is creating the main share of infested trees in recent years. As alternative to salvage logging, different technics of mechanical and manual methods of bark removal for pest control are frequently applied in areas with conservation status or in protective forests that mitigate or prevent the impact of a natural hazard. To test the field applicability of bark removal technics, we compare economic costs between manual debarking and bark gouging and evaluate how pest control and non-target biodiversity are affected from bark gouging if the phloem is cut with decreasing accuracy mirroring practical application by forest enterprises. Based on data of an experimental design we show, that bark gouging is twice as fast as manual debarking. From complete debarked P. abies logs no I. typogrphus emerged (pest control efficiency of 100%) but diversity of other emerging beetle species is reduced near zero. If bark gouging is conducted with high accuracy (phloem sufficiently cut in more than half of stripes) pest control efficiency is 99.9% and for low accuracy (below 50%) pest control efficiency is still 95.7%. Non-target beetle diversity increases with reduced accuracy. Bark gouging combines sufficed pest control with biodiversity conservation at lower economic costs than manual debarking and can thus be recommended for protected areas and protective forests, in particular.
Assessing the impacts of natural disturbance on the functioning of complex forest systems are imperative in the context of global change. The unprecedented rate of contemporary species extirpations, coupled with widely held expectations that future disturbance intensity will increase with warming, highlights a need to better understand how natural processes structure habitat availability in forest ecosystems. Standardised typologies of tree-related microhabitats (TreMs) have been developed to facilitate assessments of resource availability for multiple taxa. However, natural disturbance effects on TreM diversity have never been assessed. We amassed a comprehensive dataset of TreM occurrences and a concomitant 300-year disturbance history reconstruction that spanned large environmental gradients in temperate primary forests. We used nonlinear analyses to quantify relations between past disturbance parameters and contemporary patterns of TreM occurrence. Our results reveal that natural forest dynamics, characterised
European forest ecosystems are increasingly exposed to stressors such as storm, drought episodes and mass attack of forest insect pests. Sustainable forest management requires a fundamental understanding of causal relationships between forest structures and the occurrence of disturbance events, as well as a well-functioning transfer of scientific knowledge into practice. Risk or predisposition assessment, phenological models or prediction of deficits in stand water supply can serve as decision support for prophylactic and protective measures in forestry. This overview addresses the theoretical approaches to insect pest-related mortality in forests that form the basis for such models. Many insect herbivore species benefit from increased temperatures and drought. For example, there is a clear correlation between bark beetle infestation and summer temperatures, storm damage and precipitation deficits. Drought stress is one of the main factors predisposing conifer forests to bark beetle infestation and significantly impacts interactions among Picea abies , Ips typographus and its associated ophiostomatoid fungi. A multi-year study focused on the effects of drought on the defence capacity and attractiveness of Norway spruce to I. typographus . The empirical dataset gained in field and laboratory experiments provides new insights into defence responses of this important tree species against biotic infestations under drought.
An ongoing loss of Europe’s old-growth forests urgently calls for improving our understanding of native biodiversity response to habitat changes. Studies disentangling the effects of habitat quantity, quality, and continuity on species diversity are rare, however, understanding the differences between these effects is crucial for forest management and conservation efforts. Here, we investigated the influence of habitat quantity, quality, and continuity on the total and red-listed species richness of wood-inhabiting fungi in old-growth mountain Norway spruce (Picea abies Karst.) forest in Central Europe. The fruitbody-based mycological survey conducted on permanent plots was combined with the measurements of forest structural characteristics such as deadwood volumes (indicating habitat quantity), dimensions, and decay stages (indicating habitat quality). Additionally, precise dendrochronological measurements were used to estimate the mean age of five oldest trees and the number of >250 years-old-trees (i.e., those that survived a probable logging activity about 250 years ago) as indicators of habitat continuity. Our results showed the total species richness of wood-inhabiting fungi to be best correlated with habitat quantity (volume of low snags and lying deadwood), while the red-listed species richness was best explained by habitat continuity indicated by the number of >250 years-old-trees. Our study provides novel evidence regarding uninterrupted habitat continuity being crucial in supporting red-listed fungal species. Stands with preserved habitat continuity (e.g., the absence of clearcutting and deforestation) as well as old-growth stands with long habitat history should be prioritised for conservation. Greater degree of retention forestry practices should be required in production forests to preserve habitat continuity. Our study shows that such decisions are likely to lead to positive effects that can persist for centuries.
Forest disturbances are intensifying globally, yet regional drivers of these dynamics remain poorly understood. We investigated recent disturbance intensities in Norway spruce (Picea abies L.) forests in Slovakia (Central Europe) with different management objectives in 2000-2017 based on Landsat imagery. We focused on 122 strict reserves without any management, their actively managed surroundings (500 m and 2000 m buffers), and managed production forests beyond the buffer areas. We used generalized additive mixed models to test for differences in temporal trends of disturbance intensity among these management categories. We found that disturbance intensity was increasing in all management categories during the studied period. The increase was more pronounced in the managed forests (compound annual disturbance rate 1.76% year −1) and the 2000 m buffer (2.21% year −1) than in the strict reserves (0.58% year −1). The predicted cumulative disturbance during the 18-year period was 9.9% in the reserves and 30.5% in the 2000 m buffer. We found that forests in nature reserves can be more resistant to disturbances than forests managed for timber production, despite management efforts to control disturbances in managed forests. Our findings can help reconcile the different perceptions of natural disturbances and their management in Central Europe and support climate-adapted management strategies that consider natural disturbances as an indispensable component of ecosystem dynamics.
Although natural disturbances are likely to occur more frequently and be more severe in future as a result of climate change, we have little evidence concerning the effect of disturbance size and severity on species diversity. We aimed to compare effects of varying size and severity of natural disturbances on bird species composition in the non-intervention area of Š umava National Park, Czech Republic. For this purpose, we surveyed bird communities in 1) small-and 2) large-scale disturbance, 3) enclaves of live trees in large-scale disturbance areas, and 4) non-disturbed forests. Furthermore, we used habitat characteristics to identify structural factors affecting species composition of bird communities. Birds were sampled by the point count method during the 2021 breeding season and analysed using linear models. Additionally, we use principal component analysis (PCA) to characterize four defined disturbance classes using habitat characteristics. The most important habitat characteristics for bird communities are structural complexity, live tree density, and understorey cover. Small-scale disturbances increased structural complexity of a forest and had a generally positive effect on birds. Both small-and large-scale disturbances supported species nesting on the ground and shrub layer. In contrast, large-scale disturbances negatively affected canopy nesting and specialist species. This likely was due to a reduction of small-scale habitat heterogeneity with increasing disturbance severity. High-severity disturbance changes structurally rich forests to rather uniform, open-canopy habitats that are temporally unsuitable for closed-canopy birds. On the other hand, low-severity disturbance enhances large-scale habitat heterogeneity and maintains suitable habitat for species of closed-canopy forest, including some specialist species.
Tropical cyclones (TCs) are common disturbance agents in tropical and subtropical latitudes. With global warming, TCs began to move to northern latitudes, with devastating effects on boreal forests. However, it remains unclear where and when these extraordinary events occur and how they affect forest structure and ecosystem functioning. Hence knowing which geomorphological features, landforms, and forest types are most susceptible to severe wind disturbance is vital to better predict the future impacts of intensifying tropical cyclones on boreal forests. In October 2015, catastrophic TC Dujuan hit the island of Sakhalin in the Russian Far East. With a wind speed of 63 m·s-1, it became the strongest wind recorded in Sakhalin, damaging >42,000 ha of native forests with different levels of severity. We used high-resolution RGB satellite images, DEM-derived geomorphological patterns, and the U-Net-like convolutional neural network to quantify the damaged area in specific landform, forest type, and windthrow patch size categories. We found that large gaps (>1 ha) represent >40 % of the damaged area while small gaps (<0.1 ha) only 20 %. The recorded canopy gaps are very large for the southern boreal forest. We found that the aspect (slope exposure) is the most important in explaining the damaged area, followed by canopy closure and landform type. Closed-canopy coniferous forests on steep, west-facing slopes (typical of convex reliefs such as ridges, spurs, and peaks) are at a much higher risk of being disturbed by TCs than open-canopy mountain birch forests or coniferous forests and broadleaved riparian forests in concave reliefs such as valley bottoms. We suggest that the projected ongoing poleward migration of TCs will lead to an unprecedentedly large area of disturbed forest, which results in complex changes in forest dynamics and ecosystem functioning. Our findings are crucial for the development of mitigation and adaptation strategies under future changes in TC activity.
Tropical cyclones (TCs) are common disturbance agents in tropical and subtropical latitudes. With global warming, TCs began to move to northern latitudes, with devastating effects on boreal forests. However, it remains unclear where and when these extraordinary events occur and how they affect forest structure and ecosystem functioning. Hence knowing which geomorphological features, landforms, and forest types are most susceptible to severe wind disturbance is vital to better predict the future impacts of intensifying tropical cyclones on boreal forests. In October 2015, catastrophic TC Dujuan hit the island of Sakhalin in the Russian Far East. With a wind speed of 63 m·s−1, it became the strongest wind recorded in Sakhalin, damaging >42,000 ha of native forests with different levels of severity. We used high-resolution RGB satellite images, DEM-derived geomorphological patterns, and the U-Net-like convolutional neural network to quantify the damaged area in specific landform, forest type, and windthrow patch size categories. We found that large gaps (>1 ha) represent >40 % of the damaged area while small gaps (<0.1 ha) only 20 %. The recorded canopy gaps are very large for the southern boreal forest. We found that the aspect (slope exposure) is the most important in explaining the damaged area, followed by canopy closure and landform type. Closed-canopy coniferous forests on steep, west-facing slopes (typical of convex reliefs such as ridges, spurs, and peaks) are at a much higher risk of being disturbed by TCs than open-canopy mountain birch forests or coniferous forests and broadleaved riparian forests in concave reliefs such as valley bottoms. We suggest that the projected ongoing poleward migration of TCs will lead to an unprecedentedly large area of disturbed forest, which results in complex changes in forest dynamics and ecosystem functioning. Our findings are crucial for the development of mitigation and adaptation strategies under future changes in TC activity.
Investigating the disturbance regimes of unharvested forests helps us understand their past, present, and future trajectory and gives us a model for forest management. It can also clarify the relative importance of small-scale gap dynamics versus more severe disturbances. Here we used tree rings to examine the recruitment patterns, growth dynamics, and disturbance chronologies of American beech (Fagus grandifolia), sugar maple (Acer saccharum), and eastern hemlock (Tsuga canadensis) in A.B. Williams Woods, an old-growth forest in Ohio, USA, over the past 250 years. We found that beech and sugar maple recruitment peaked around 1900 and continued through the 1900s, while hemlock recruitment peaked during 1825–1875, then declined and effectively ended in the early 1900s. Hemlock grew fastest during the 1800s according to ring width and basal area increment, while sugar maple ring width surpassed beech and hemlock in the 1900s. All three species showed a dramatic increase in growth from 1980 to 2010. Beech and sugar maple established regardless of canopy gaps, but 73% of hemlocks originated in gaps. In most decades, <10% of trees experienced gap recruitment or growth release, suggesting that ongoing, endogenous canopy mortality was the primary disturbance shaping this forest. However, a more severe forest-wide disturbance occurred during the 1980s–1990s when the scale insect causing beech bark disease was introduced, with greater than 30% of living trees showing growth releases in those decades. Another synchronous release occurred in the 1930s when blight-killed chestnuts were removed; 16% of trees showed releases. Both of these intermediate-severity disturbances involved human introduction of invasive species. Thus, we documented a natural disturbance regime of small-scale gap dynamics, punctuated by more severe anthropogenic disturbances in the twentieth century. These relatively frequent, intermediate-severity events probably mean that the forest’s current composition is non-equilibrial. Hemlock may continue to decline while beech maintains its dominance by constant regeneration in both gaps and shade, and by responding to disturbance with root suckering and growth pulses. The codominance of sugar maple may be relatively recent, and perhaps temporary, as we found little sugar maple recruitment before 1875 or after 1950, and three times fewer sugar maple saplings now than in the early 1900s. Despite being protected as a park, the development of this old-growth forest has been shaped more by disease-causing invasive species than natural disturbances over the past century. This result emphasizes the pervasiveness of human impacts even in communities we look to as examples of natural pattern and process.
Outbreaks of the eruptive Eurasian spruce bark beetle (Ips typographus) have led to extensive mortality of European Norway spruce (Picea abies) forests causing severe economic losses, but also initiating forest succession and regeneration. Establishment and reproduction of I. typographus and its assemblage of microbial partners is initiated by pheromone-mediated mass attacks to circumvent the host's formidable chemical and anatomical defenses. However, in contrast to its host tree, which is poorly adapted to climatic conditions outside its natural habitat, I. typographus benefits from a warm and dry environment. Increasing temperatures promote multivoltine bark beetle populations; yet, their consequences for hibernation and diapause are still unclear. Existing knowledge of I. typographus has focused on individual aspects of the bark beetle development and host defense. To gain an improved understanding of climate-driven ecological changes in forest ecosystems, the complex interplay between climate change, beetle phenology, associated microbes, and tree physiology should be studied under natural field and laboratory conditions.
The availability of global digital elevation models (DEMs) from multiple time points allows their combination for analysing vegetation changes. The combination of models (e.g., SRTM and TanDEM-X) can contain errors, which can, due to their synergistic effects, yield incorrect results. We used a high-resolution LiDAR-derived digital surface model (DSM) to evaluate the accuracy of canopy height estimates of the aforementioned global DEMs. In addition, we subtracted SRTM and TanDEM-X data at 90 and 30 m resolutions, respectively, to detect deforestation caused by bark beetle disturbance and evaluated the associations of their difference with terrain characteristics. The study areas covered three Central European mountain ranges and their surrounding areas: Bohemian Forest, Erzgebirge, and Giant Mountains. We found that vertical bias of SRTM and TanDEM-X, relative to the canopy height, is similar with negative values of up to −2.5 m and LE90s below 7.8 m in non-forest areas. In forests, the vertical bias of SRTM and TanDEM-X ranged from −0.5 to 4.1 m and LE90s from 7.2 to 11.0 m, respectively. The height differences between SRTM and TanDEM-X show moderate dependence on the slope and its orientation. LE90s for TDX-SRTM differences tended to be smaller for east-facing than for west-facing slopes, and varied, with aspect, by up to 1.5 m in non-forest areas and 3 m in forests, respectively. Finally, subtracting SRTM and NASA DEMs from TanDEM-X and Copernicus DEMs, respectively, successfully identified large areas of deforestation caused by hurricane Kyril in 2007 and a subsequent bark beetle disturbance in the Bohemian Forest. However, local errors in TanDEM-X, associated mainly with forest-covered west-facing slopes, resulted in erroneous identification of deforestation. Therefore, caution is needed when combining SRTM and TanDEM-X data in multitemporal studies in a mountain environment. Still, we can conclude that SRTM and TanDEM-X data represent suitable near global sources for the identification of deforestation in the period between the time points of their acquisition.
Mountain forests provide a wide range of ecosystem services, including carbon sequestration and protection from natural hazards. Forest cover in the European Alps has increased over the last century, but in recent years, these forests have experienced an increasing rate of natural disturbances by agents such as windthrow, bark beetle outbreaks, and forest fires. These disturbances pose a challenge for forest management, making it important to understand how site and stand characteristics, land use legacies and recent management influence disturbance probability. We combined a dataset of forest disturbances detected from space with in-situ forest management records, allowing us to differentiate between different types of disturbances for the Canton of Graubünden, Switzerland, in the years 2005–2018. The resulting dataset of over 28′000 attributed disturbance patches (corresponding to a disturbed forest area of ca. 23′600 ha) was combined with information on topography, forest structure, and historical forest cover. A machine-learning approach was used to investigate the non-linear and interacting relationships between potential drivers and disturbance occurrence. Natural disturbances (especially windthrow and bark beetle outbreaks) were most common at lower elevations, on shallow and south-facing slopes, and in even-aged, spruce-dominated stands with a closed canopy. Forests established in the 20th century were significantly more susceptible to natural disturbances than forests that were already present before 1880, which may be due to the uniform age and vertical structure of secondary forests, as well as legacy effects of former agricultural use. On the other hand, forest management more often took place in forests present before 1880. Management interventions (such as thinning) in turn increased the susceptibility to natural disturbances in the short term. This finding emphasizes the need to balance short-term increases in disturbance susceptibility with long-term benefits in forest resilience when planning management interventions in mountain forests. Our findings highlight the importance of considering multiple interactive drivers, including management and land-use history, for understanding forest disturbance regimes.
Evropské lesy poskytovaly lidské společnosti po staletí mnohé ekosystémové služby a generovaly značné ekonomické hodnoty. Některé z těchto benefitů jsou stále více ohrožovány změnou klimatu, která znásobuje vliv různých disturbančních činitelů, jako jsou např. kůrovci. Zranitelnost evropských lesů nepříznivě ovlivnil i jejich dlouhodobý
management. Například smrk ztepilý byl pro svůj rychlý růst a příznivé technické vlastnosti v minulých stoletích hojně vysazován mimo areál svého přirozeného rozšíření. Tím vznikly rozsáhlé plochy tzv. sekundárních smrkových lesů, které měly stále větší problémy se zdravotním stavem a vitalitou, a byly náchylné k poškození činiteli, jako je vítr, sucho a kůrovec. Tato studie má za cíl pomoci při tvorbě evropských a národních lesnických strategií, přispět k lepšímu pochopení působení kůrovce na lesy, a poskytnout vědecká východiska pro lesnické strategie umožňující zvládat současné kůrovcové kalamity.
Disentangling the long-term changes in forest disturbance dynamics provides a basis for predicting the forest responses to changing environmental conditions. The combination of multidisciplinary records can offer more robust reconstructions of past forest disturbance dynamics. Here we link disturbance histories of the central European mountain spruce forest obtained from dendrochronological and palaeoecological records (fossil pollen, sedimentary charcoal, bark beetle remains and geochemistry) using a small glacial lake and the surrounding forest in the Šumava National Park (Czech Republic). Dendrochronological reconstructions of disturbance were created for 300-year-long records from 6 study plots with a minimum of 35 trees analyzed for the abrupt growth increases (releases) and rapid early growth rates, both indicative of disturbance events. High-resolution analysis of lake sediments were used to reconstruct 800-year long changes in forest composition and landscape openness (fossil pollen), past fire events (micro- and macroscopic charcoal), bark beetle occurrence (fossil bark beetle remains), and erosion episodes (geochemical signals in the sediment) potentially resulting from disturbance events.
Tree-ring data indicate that disturbances occurred regularly through the last three centuries and identify a most intensive period of disturbances between 1780 and 1830 CE. Geochemical erosion markers (e.g. K, Zr, % inorganic) show greater flux of catchment sediment and soils in the periods 1250–1400 and 1450–1500 CE, before a substantial shift to a more erosive regime 1600–1850 and 1900 CE onwards. Pollen records demonstrate relatively small changes in forest composition during the last 800 years until the beginning of the 20th century, when there was decrease in Picea. Fossil bark beetle remains indicate continuous presence of bark beetles from 1620s to 1800s, and charcoal records suggest that more frequent fires occurred during the 18th century. Each of the dendrochronological, palaeoecological and sedimentological records provide a unique perspective on forest disturbance dynamics, and combined offer a more robust and complete record of disturbance history. We demonstrate that sedimentary proxies originating from the lake catchment mirror the forest disturbance dynamics recorded in the tree-rings. The multidisciplinary records likely record forest disturbances at different spatial and temporal scales revealing different disturbance characteristics. Integrating these multidisciplinary datasets demonstrates a promising way to obtain more complete understanding of long-term disturbance dynamics. However, integrating datasets with variable spatial and temporal influence remains challenging. Our results indicated that multiple disturbance factors, such as windstorms, bark beetle outbeaks and fires, may occur simultaneously creating a complex disturbance regime in mountain forests, which should be considered in forest management and conservation strategies.
Browsing damage by ungulates is among the most decisive factors affecting the establishment and growth of young trees. In recent decades, ungulate populations have been expanding in the Northern Hemisphere; impairment of tree regeneration by their activity is an increasing problem. Herbivore-induced changes in tree regeneration may alter the composition and biodiversity of the future tree stand. In this study we determined where young trees can leave the seedling bank and succeed to higher forest strata in a protected natural forest that is under strong herbivore pressure. We studied rowan (Sorbus aucuparia) regeneration in a subalpine spruce forest growing in a strictly protected area of Babia Góra National Park (Western Carpathians). Rowan is one of the most palatable forest species, so browsing can significantly limit its growth. We predicted that factors, that restrict the movement of red deer (Cervus elaphus), decrease their visits in some forest patches, which will result in a higher share of rowan saplings. We also considered two other factors that can affect the distribution of rowan saplings: light availability and distance to maternal trees. In particular, we tested whether the occurrence of rowan saplings was related to: (i) slope angle, amount of logs lying on the forest floor, and distance to the hiking trails; (ii) distance to fruit-bearing trees; and (iii) canopy openness. The results confirmed our main predictions concerning the relation between the occurrence of palatable tree saplings and the availability of a forest area to ungulates. Factors related to the availability of terrain to red deer significantly influenced the distribution of rowan saplings taller than 1 m. The probability of rowan sapling occurrence increased when the amount of logs was higher and the distance to hiking trails was shorter. Slope had a significant negative impact on sapling occurrence. We found no effect of proximity of fruit-bearing rowan trees or canopy gap area. Thus, in the natural forest, the likelihood that young palatable trees will make the transition from seedlings to taller saplings seems to be determined mainly by factors related to ungulate activity. This suggests that the increase of ungulate populations and their browsing behavior will affect the species composition and spatial structure of future tree stands.
Zusammenfassung Bergmischwälder aus Fichte (Picea abies (L.) Karst), Weißtanne (Abies alba Mill.) und Europäischer Rot-buche (Fagus sylvatica) bedecken in Europa eine Gesamtfläche von mehreren Millionen Hektar. Sie verbinden die Buchenwaldgesellschaften im Tiefland mit den fichtendominierten, alpinen Waldtypen. Aufgrund ihrer Höhenzonierung sind diese Wälder besonders von den Auswirkungen des Klimawandels betroffen. Darüber hinaus ermöglichen neue Erschließungstechniken innovative Möglichkeiten einer intensivierten Bergwaldbewirtschaftung. Da jedoch wenig über die langfristige Entwicklung der Produk-tivität dieser Waldsysteme in Europa bekannt ist, sind belastbare Informationen über Produktivität und Anpassungsmöglichkeiten erforderlich, um nachhaltige Bewirtschaftungspläne zu entwickeln. Vor die-sem Hintergrund wurden in der vorliegenden Arbeit 59 langfristige Bergmischwald-Versuchsflächen entlang eines Höhengradienten in Europa untersucht. Der periodische jährliche Volumenzuwachs (iV) auf Bestandsebene, sowie die artspezifische Produktivitätsentwicklung in den letzten 30 Jahren bilde-ten den Schwerpunkt der Untersuchung. So konnte im Rahmen der Studie erstmals eine durchschnittli-che Produktivität der gemäßigten Bergmischwälder Europas ermittelt werden (9,3 m³ha-1 a-1 über alle Bereiche hinweg). Die Entwicklung zeigt, dass die Produktivität auf Bestandsniveau in den letzten Jahr-zehnten insgesamt konstant geblieben ist. Die artenspezifische Produktivitätsanalyse zeigt, dass der iV der Fichte zu Beginn der Studie (1980) noch etwa 14 m 3 ha-1 a-1 betrug und heute knapp 11 m 3 ha-1 a-1 beträgt. Mit knapp 7 m 3 ha-1 a-1 ist der iV der Tanne der niedrigste der drei Baumarten zu Beginn der Untersuchungsperiode. Das Wachstum der Tanne steigt jedoch signifikant auf über 11 m³ha-1 a-1 und ist damit heute die produktivste Baumart in den Berg-Mischwäldern Europas. Die Buche wächst über den gesamten Untersuchungszeitraum mit einer Wachstumsrate von ca. 8,2 m³ha-1 a-1. Der Rückgang der Produktivität der Fichte in den letzten 30 Jahren konnte somit durch eine Steigerung der Produktivität der Tanne weitgehend kompensiert werden und erklärt den konstanten iV auf Bestandsebene. Folglich konstatieren wir stabile Volumenzuwächse in Bezug auf den Klimawandel. Damit scheint eine kontinu-ierliche Versorgung mit Ökosystemgütern aus Berg-Mischwäldern gewährleistet zu sein. Summary Mixed mountain forests of Norway spruce (Picea abies (L.) Karst), silver fir (Abies alba Mill.) and Euro-pean beech (Fagus sylvatica) cover a total area of several million hectares in Europe. They connect the beech forest communities in the lowlands with the spruce-dominated alpine forest types. Due to their height zoning, these forests are particularly affected by climate change. In addition, new development techniques enable innovative possibilities for intensified mountain forest management. However, as little is known about the long-term development of the productivity of these forest systems in Europe, reliable information on productivity and adaptation options is required in order to develop sustainable management plans. Against this background, 59 long-term mixed mountain forest experimental plots along a height gradient in Europe were investigated in this study. The periodic annual volume increment (iV) at stand level as well as the species-specific productivity development over the last 30 years formed the focus of the study. For the first time, an average productivity of Europe's temperate mixed mountain forests (9.3 m³ha-1a-1 across all areas) could be determined within the framework of the study. This development shows that overall productivity at stand level has remained constant over the past decades. The species-specific productivity analysis showed that the iV of spruce at the beginning of Hilmers et al.: Zur Produktivität von Bergmischwäldern aus Picea abies, Abies alba und Fagus sylvatica in Europa DVFFA-Sektion Ertragskunde 25 Beiträge zur Jahrestagung 2018 the study (1980) was still about 14 m 3 ha-1 a-1 and today is just under 11 m 3 ha-1 a-1. With just under 7 m 3 ha-1 a-1 , the iV of fir is the lowest of the three tree species at the beginning of the study period. However , the growth of fir rises significantly to over 11 m 3 ha-1 a-1 and is therefore today the most productive tree species in the mixed mountain forests of Europe. Beech grows at a growth rate of approx. 8.2 m³ha-1 a-1 over the entire period under study. The decline in spruce productivity over the last 30 years has thus been largely compensated by an increase in fir productivity and explains the constant iV at stand level. Consequently, we observe stable volume increases in relation to climate change. This seems to guarantee a continuous supply of ecosystem goods from mixed mountain forests.
Information on the historical background of the present forest conditions is needed for proper decisions on forest management. Disturbances play a major role in the formation of forest structure and composition. This paper compares the present break-up of mountain spruce stands in the Bohemian Forest (in the Šumava Protected Landscape Area) with conditions during their initiation using dendrochronological techniques. On three selected localities we established two study plots within relatively old stands of unknown origin. Stands were recently broken up by a windstorm. The present situation was described by diameter and decay class distribution. To describe the situation at the stand initiation, we cored at least 40 stems on each plot to get the age structure and growth series of trees. Disturbances were marked by discovering synchronous releases on tree-ring series. Main population waves were initiated in association with severe disturbances during a relatively short period, leading to the establishment of relatively even-aged, homogeneously looking stands. The disturbancees were synchronized between plots and ac-counted for by historically known windstorms or bark beetle outbreaks; notwithstanding, logging as a disturbance factor is also particularly possible.
Natural disturbances are among the most important factors that shape forest dynamics and forest landscapes. However, the natural disturbance regime of Norway spruce (Picea abies (L.) Karst.) forests in Europe is not well understood. We studied the disturbance regimes in three forest reserves in Bulgaria (Parangalitsa, Bistrishko branishte, and Beglika), which are representative of the range of conditions typical for P. abies ecosystems in central and southern Europe. Our data indicated that large-scale disturbances were most numerous in forests that were between 120 and 160 years old, those with unimodal diameter at breast height (DBH) distributions, and especially those located in vulnerable topographic settings. Wind disturbances ranged up to 60 ha, followed in one case by a 200 ha Ips typographus (Linnaeus, 1758) outbreak. Older forests and those with more complex structures (i.e., reverse-J DBH) were characterized by numerous small gaps but were also affected by a few larger disturbances. In some old-growth forests at highly productive sites, gaps could be so numerous that the long-term existence of old trees may become an exception. Over the past centuries, the natural range of variability of these Norway spruce forests in Bulgaria appears to have been shaped mostly by wind and bark beetle disturbances of various sizes. © 2015, National Research Council of Canada. All rights Reserved.
Much of our understanding of natural forest dynamics in the temperate region of Europe is based on observational studies in old-growth remnants that have emphasized small-scale gap dynamics and equilibrium stand structure and composition. Relatively little attention has been given to the role of infrequent disturbance events in forest dynamics. In this study, we analyzed dendroecological data from four stands and three windthrow patches in an old-growth landscape in the Dinaric Mountains of Bosnia and Herzegovina to examine disturbance history, tree life history traits, and compositional dynamics. Over all stands, most decades during the past 340 years experienced less than 10% canopy loss, yet each stand showed evidence of periodic intermediate-severity disturbances that removed > 40% of the canopy, some of which were synchronized over the study area landscape. Analysis of radial growth patterns indicated several life history differences among the dominant canopy trees; beech was markedly older than fir, while growth patterns of dead and dying trees suggested that fir was able to tolerate longer periods of suppressed growth in shade. Maple had the fastest radial growth and accessed the canopy primarily through rapid early growth in canopy gaps, whereas most beech and fir experienced a period of suppressed growth prior to canopy accession. Peaks in disturbance were roughly linked to increased recruitment, but mainly of shade-tolerant beech and fir; less tolerant species (i.e., maple, ash, and elm) recruited successfully on some of the windthown sites where advance regeneration of beech and fir was less abundant. The results challenge the traditional notions of stability in temperate old-growth forests of Europe and highlight the nonequilibrial nature of canopy composition due to unique histories of disturbance and tree life history differences. These findings provide valuable information for developing natural disturbance-based silvicultural systems, as well as insight into maintaining less shade-tolerant, but valuable broadleaved trees in temperate forests of Europe.
A methodology is proposed for developing a disturbance chronology in stands by identifying the probable date of canopy accession for each sample tree. Canopy disturbance intensity is defined as the percentage of sample trees with canopy accession events in each decade. Rotation periods for disturbances of various intensities are calculated from the chronology. The method was evaluated using 893 increment cores from 70 plots in northern hardwood stands of W Upper Michigan. Average disturbance rate for all plots and decades was 5.7-6.9% of land area per decade, with an implied average canopy tree residence time of 145-175 yr. -from Authors
Questions: How have the historical frequency and severity of natural disturbances
in primary Picea abies forests varied at the forest stand and landscape level
during recent centuries? Is there a relationship between physiographic attributes
and historical patterns of disturbance severity in this system?
Location: Primary P. abies forests of the Eastern Carpathian Mountains, Romania;
a region thought to hold the largest concentration of primary P. abies forests
in Europe’s temperate zone.
Methods: We used dendrochronological methods applied to many plots over a
large area (132 plots representing six stands in two landscapes), thereby providing
information at both stand and landscape levels. Evidence of past canopy disturbance
was derived from two patterns of radial growth: (1) abrupt, sustained
increases in growth (releases) and (2) rapid early growth rates (gap recruitment).
Thesemethods were augmented with non-metricmultidimensional scaling
to facilitate the interpretation of factors influencing past disturbance.
Results: Of the two growth pattern criteria used to assess past disturbance, gap
recruitment was the most common, representing 80% of disturbance evidence
overall. Disturbance severities varied over the landscape, including stand-replacing
events, as well as low- and intermediate-severity disturbances. More than
half of the study plots experienced extreme-severity disturbances at the plot
level, although they were not always synchronized across stands and landscapes.
Plots indicating high-severity disturbances were often spatially clustered
(indicating disturbances up to 20 ha), while this tendency was less clear for lowand
moderate-severity disturbances. Physiographic attributes such as altitude
and land form were only weakly correlated with disturbance severity. Historical
documents suggest windstorms as the primary disturbance agent, while the role
of bark beetles (Ips typographus) remains unclear.
Conclusions: The historical disturbance regime revealed in this multi-scale
study is characterized by considerable spatial and temporal heterogeneity,which
could be seen among plots within stands, among stands within landscapes and
between the two landscapes. When the disturbance regime was evaluated at
these larger scales, the entire range of disturbance severity was revealed within
this landscape.
Papers aims at definition of several attitudinal landscape zones in Bohemian forest, Czech republic, reflecting different kinds of human impact in prehistory and history.
Heavy natural disturbance in large protected areas of former commercial forests increasingly evokes European parliaments to call for management intervention because a loss of habitats and species is feared. In contrast, natural early successional habitats have recently been recognised as important for conservation. Current knowledge in this field mostly results from studies dealing only with selected taxa. Here we analyse the success of species across 24 lineages of three kingdoms in the Bavarian Forest National Park (Germany) after 15 years of a European spruce bark beetle (Ips typographus L.) outbreak that led to rapid canopy opening. Using indicator species analysis, we found 257 species with a significant preference for open forests and 149 species with a preference for closed forests, but only 82 species with a preference for the stand conditions transitional between open and closed forests. The large number of species with a preference for open forests across lineages supports the role of this bark beetle as a keystone species for a broad array of species. The slowdown of the outbreak after 15 years in the core zone of the national park resulted in less than half of the area being affected, due to variability in stand ages and tree species mixtures. Our case study is representative of the tree species composition and size of many large protected montane areas in Central European countries and illustrates that (1) natural disturbances increase biodiversity in formerly managed forests and (2) a montane protected area spanning 10,000 ha of low range mountains is likely sufficient to allow natural disturbances without a biased loss of closed-forest species.
Forests dominated by Douglas-fir and western hemlock in the Pacific Northwest of the United States have strongly influenced concepts and policy concerning old-growth forest conservation. Despite the attention to their old-growth characteristics, a tendency remains to view their disturbance ecology in relatively simple terms, emphasizing infrequent, stand-replacing (SR) fire and an associated linear pathway toward development of those old-growth characteristics. This study uses forest stand- and age-structure data from 124 stands in the central western Cascades of Oregon to construct a conceptual model of stand development under the mixed-severity fire regime that has operated extensively in this region. Hierarchical clustering of variables describing the age distributions of shade-intolerant and shade-tolerant species identified six groups, representing different influences of fire frequency and severity on stand development. Douglas-fir trees > 400 years old were found in 84% of stands, yet only 18% of these stands (15% overall) lack evidence of fire since the establishment of these old trees, whereas 73% of all stands show evidence of at least one non-stand-replacing (NSR) fire. Differences in fire frequency and severity have contributed to multiple development pathways and associated variation in contemporary stand structure and the successional roles of the major tree species. Shade-intolerant species form a single cohort following SR fire, or up to four cohorts per stand in response to recurring NSR fires that left living trees at densities up to 45 trees/ha. Where the surviving trees persist at densities of 60-65 trees/ha, the postfire cohort is composed only of shade-tolerant species. This study reveals that fire history and the development of old-growth forests in this region are more complex than characterized in current stand-development models, with important implications for maintaining existing old-growth forests and restoring stands subject to timber management.
We investigated the role of abiotic factors in controlling patterns of long- term windthrow in the pristine coastal temperate rain forests of southeast Alaska. Our objectives were to test the extent to which long-term patterns of windthrow can be predicted spatially at the landscape scale by using four abiotic factors (slope, elevation, soil stability, and exposure to prevailing storm winds), evaluate landform influence on windthrow, and compare stand age and structural characteristics in areas prone to and protected from windthrow. On Kuiu Island, southeast Alaska, we used field validation photo-interpretation procedures to identify forest patches likely to be of windthrow origin. A spatially explicit logistic model was then built from the windthrow data and other GIS data layers, based on slope, elevation, soil type, and exposure to prevailing storm winds. Landform influence on patterns of windthrow was examined by evaluating correct model classification by landform type. The model was cross-validated by extrapolating the Kuiu model coefficients to nearby Zarembo Island, and comparing model predictions to an independent large-scale windthrow data set. The model correctly classified 72% of both windthrown and non- windthrown forest. Field data collected in areas most and least prone to windthrow on Kuiu suggest that structural and age characteristics, as well as forest development stages, vary with the probability of windthrow across the landscape. We conclude that small-scale (partial-canopy) disturbance processes predominate in areas least prone to windthrow, and that large-scale stand-replacement disturbance processes predominate in areas most prone to windthrow. Our work suggests that a spatially predictable long-term wind-damage gra- dient exists on Kuiu Island. Before this research, gap-phase disturbances have been em- phasized as the dominant disturbance process controlling forest dynamics in North American coastal temperate rain forests. We conclude that there is less naturally occurring old-growth forest regulated by gap-phase succession than previously believed, and that catastrophic windthrow is an important process driving forest development in southeast Alaska. To date, most timber harvest on Kuiu Island has been concentrated in storm-protected areas where gap-phase processes (old-growth forests) predominate; future management activities could be tailored to consider long-term natural disturbance patterns to better maintain historical ecosystem function.
An intensive bark beetle outbreak occurred in 1993–1998 in the Tatra mountains between Slovakia and Poland. In the Slovak part of the outbreak practices consisted of: no action prior to 1994, intensive pest control management (trap trees, insecticides, salvage cutting) from 1995–1996, active differentiated approach (control measures according to the zonation of attacked stands) combined with intensive use of pheromone traps from 1997–1998. In Poland, the outbreak was mostly located in reserve areas where pest management or other activities were prohibited. Despite the use of intensive pest management measures, tree mortality was not significantly decreased in the Slovak region during the peak outbreak years of 1995 and 1996. Classical forest protection led to an increase in attractiveness of forest edges to bark beetles which could disperse to these areas from locations where no control measures were practiced. Unfavourable weather for bark beetles led to a rapid decrease in tree mortality in both parts of the study area.
Forest insects and pathogens are the most pervasive and important agents of disturbance in North American forests, affecting an area almost 50 times larger than fire and with an economic impact nearly five times as great. The same attributes that result in an insect herbivore being termed a "pest" predispose it to disruption by climate change, particularly global warming. Although many pest species have co-evolved relationships with forest hosts that may or may not be harmful over the long term, the effects on these relationships may have disastrous consequences. We consider both the data and models necessary to evaluate the impacts of climate change, as well as the assessments that have been made to date. The results indicate that all aspects of insect outbreak behavior will intensify as the climate warms. This reinforces the need for more detailed monitoring and evaluations as climatic events unfold. Luckily, we are well placed to make rapid progress, using software tools, databases, and the models that are already available.
Information on historical disturbances is vital to our understanding of current forest conditions. Dendro chronological methods provide one means of reconstructing disturbance histories in temperate and boreal forests. In particular, the dates of significant growth releases recorded on surviving trees provide strong inferential evidence of past disturbance events. The most common method of detecting releases (the percent-increase method) expresses the postevent growth increase as a percentage of the preevent rate. Despite its widespread use, the method is known to be overly sensitive at low rates of prior growth and overly stringent at high rates. We present an alternative method that directly follows the percent-increase method, but instead of dividing the postevent growth rate by the preevent rate, we simply subtract the two. If the difference exceeds a predetermined species-specific threshold, the event is considered a release. This absolute-increase method has convenient properties that remedy the shortcomings of the percent-increase method. We tested the validity of the absolute-increase thresholds by binary logistic regressions, and we compared the absolute- and percent-increase methods by various methods. We conclude that for the species evaluated in this study, the absolute-increase method represents an improvement over the standard percent-increase method.
The Bavarian Forest National Park in Germany has experienced infestations of bark beetle (Ips typographus L.) since the 1980s, resulting in considerable ecological loss due to the destruction of almost 5800 ha of spruce forests. Although there have been numerous investigations on the physiology and ecology of the bark beetle, until now the spatio-temporal infestation and dispersal dynamics of the bark beetle over a longer period have still not been satisfactorily understood. The understanding of the structure and the dispersal of bark beetle infestations is however of significant importance for forest management systems in order to predict the risk of outbreaks, especially in the face of climate change.
Structurally different from even-aged and balanced uneven-aged stands, irregular stands are an integral part of forested landscapes in northeastern North America. The maintenance or restoration of irregular stand structure may be desirable, especially in areas under ecosystem-based management. This can be achieved at the stand level through the implementation of irregular shelterwood systems. The objectives of this synthesis are to assemble the existing knowledge about the system, clarify the terminology in use, and discuss its place in silviculture in northeastern North America. Irregular shelterwood is compared with other regeneration methods and we propose a classification based on three variants. This silvicultural system is compatible with ecosystem-based management in forest types driven by partial stand mortality and gap dynamics and provides opportunities for maintaining old-growth forest attributes. However, it presents important challenges, especially with regards to planning, growth and yield prediction, and operational application.
1Disturbance histories derived from old-growth forest remnants in Europe and eastern North America have shaped many of our current theories of forest dynamics and succession. Yet the small size typical of these remnants suggests they might not capture the full range of variability that may emerge at larger scales.2We investigated the frequency and severity of natural disturbance in a 2000-ha old-growth landscape (Big Reed Forest Reserve) in northern Maine, USA. Given its size, the Reserve provides an ideal opportunity to study, at multiple scales, natural forest processes in a region that has otherwise been dramatically altered by human activities. Using dendrochronological methods, we reconstructed disturbance histories for 37 randomly located plots stratified by five forest types (hardwood forests, mixed woods forests, red spruce forests, northern white-cedar seepage forests and northern white-cedar swamps).3We found no evidence of stand replacing disturbance on any plot during the last 120–280 years (depending on plot). The overall mean disturbance rate was 9.6% canopy loss per decade (median 6.5%, maximum 55%, plots pooled), yet the distribution was strongly skewed toward the lower rates.4We found little differences in disturbance rates between forest types, save a slightly lower rate in the northern white-cedar swamps. However, if we ignore forest-type classifications, we see that disturbance rates are clearly influenced by gradients in the relative abundance of component tree species, owing to species’ relative susceptibilities to particular disturbance agents.5Synthesis. Relatively low rates of canopy disturbance allow the accrual of shade-tolerant saplings. The abundance of this advance regeneration, coupled with the absence of stand-replacing disturbance, has maintained canopy dominance by shade-tolerant species in all plots, all forest types and throughout the entire landscape. Disturbance histories from individual plots coalesce to form a picture of a landscape in which pulses of moderate-severity disturbance are interposed upon a background of scattered small-scale canopy gaps. The landscape-level mosaic resulting from this disturbance regime consists of patches in various stages of structural development, not various stages of compositional succession.
Summary 1 Data from elevations ranging from mixed hardwood-conifer forest at 600 m to subalpine Abies balsamea forest at 1120 m indicate that canopy gaps are not static but expand over time due to mortality of trees at the gap margin and coalescence of gaps. Gap expansion is more frequent than gap initiation. Ultimately such disturbance patches may become more extensive than is normally considered as typical of gap-phase disturbance, but the processes of development are the same. 2 Disturbance agents involved in gap initiation tend to differ from those involved in gap expansion. Spruce beetle, dwarf mistletoe and most root diseases predominate as agents of gap initiation, while windthrow/windsnap, chronic wind stress and Armillaria root disease are important agents of gap expansion. 3 Concepts of equilibrium gap-phase dynamics and a shifting-mosaic steady state do not fully account for the dynamics of these spruce-fir forests. A spruce beetle outbreak in the late 1970s/early 1980s killed most of a cohort of dominant, emergent Picea rubens . This epidemic initiated a long-term cycle of disturbance and release that is likely to be repeated in many years when a new cohort of P. rubens becomes sufficiently large to sustain another major bark beetle outbreak. 4 Episodic disturbance agents affect long-lived, dominant species at infrequent but regular intervals (up to hundreds of years) and operate at the landscape level. Gap-phase cycles appear to be nested within the long-term cycle. Over the long term, episodic dis- turbance drives such 'nested bicycle' dynamics. 5 Spatial and temporal distribution of disturbance results not only from stochastic events such as storms, but also from host specificity of agents of disturbance, their tendency to attack certain age classes of trees, local and regional contagion, and sus- ceptibility of trees at the edge of disturbance patches.
Accurate assessment of the magnitude and frequency of extreme wind speed is of fundamental importance for many safety, engineering and reinsurance applications. We utilize the spatial and temporal consistency of the European Centre for Medium Range Forecasts ERA-40 reanalysis data to determine the frequency of extreme winds associated with wind storms over the eastern North Atlantic and Europe. Two parameters are investigated: 10-m wind gust and 10-m wind speed. The analysis follows two different view-points: In a spatially distributed view, wind-storm statistics are determined individually at each grid-point. In an integral, more generalized view, the wind-storm statistics are determined from extreme wind indices (EWI) that summarize storm magnitude and spatial extent. We apply classical peak over threshold (POT) extreme value analysis techniques (EVA) to the EWI and grid-point wind data. As a reference, a catalogue of the 200 most prominent European storms has been compiled based on available literature. The EWI-based return periods (RP) estimates of catalogue wind storms range from approximately 0.1 to 300 years, whereas grid-point-based RP estimates range from 0.1 to 500+ years. EWIs sensitive to the absolute magnitude of wind speed rank the RP of wind storms in the 1989/1990 and 1999/2000 extended winter season similarly to the RP derived from the distributed approach. The RP estimates derived from EWIs are generally higher when calculated using only land grid-points compared to RPs derived using whole domain. Both the uncertainties in EWIs and grid-point-based RPs show a greater dependence on the wind parameter used than on the uncertainty associated with the EVA for RPs less than 10 years, whereas for RPs greater than 10 years the effect of the different datasets is lower. The EWIs share up to approximately 50% of the variability of the local grid-point RPs. Copyright © 2008 Royal Meteorological Society
The influence of natural disturbance on biodiversity is poorly known in the intensively cultivated landscape of Europe. As
an example of insect disturbance we studied effects of gaps generated by outbreaks of the spruce bark beetle (Ips typographus) on biodiversity in the area of the National Park “Bavarian Forest” and compared them with openings (e.g. meadows) created
by humans in these forests. Insects were sampled using flight interception traps across twelve ecotones between edges of closed
forest, six bark beetle gaps and six meadows. The diversity and species density of true bugs and of bees/wasps increased significantly
from the closed stand to the edge, and continued to increase inside the openings at interior and exterior edges. Species density
in saproxylic beetles also increased significantly from closed forest to opening, but only across ecotones including bark
beetle gaps. Similarly, the number of critically endangered saproxylic beetles increased significantly in bark beetle gaps.
Using indicator species analysis a total of 60 species were identified as possessing a statistically significant value indicating
preference for one of the habitat types along the ecotones: 29 of them preferred gaps, 24 preferred meadows, three were characteristic
for edges of meadows, three for edges of bark beetle gaps, but only one was typical of closed forest. Most of our results
support the thesis that I.typographus fulfils the majority of criteria for a keystone species, particularly that of maintenance of biodiversity in forests. Our
results emphasize the value for the study and conservation of insect diversity of the policy of non-interference with natural
processes pursued in some protected areas. As a recommendation to forest management for increasing insect diversity even in
commercial forest, we suggest that logging in recent gaps in medium aged mixed montane stands should aim at retention of a
part of the dead wood. Planting should be avoided, to lengthen the important phase of sunlit conditions.
Large, severe disturbances drive many forest ecosystems over the long term, but pose management uncertainties when human experience with them is limited. Recent continent‐scale outbreaks of bark beetles across the temperate Northern Hemisphere have raised major concerns as to whether coniferous forests will regenerate back towards pre‐outbreak condition and meet possible reforestation objectives. To date, however, analyses of post‐outbreak regeneration across broad spatial and temporal scales have been rare, and entirely lacking for many regions.
Following a series of large, severe ( 99% overstorey mortality) outbreaks of spruce bark beetles Ips typographus in Central Europe, we capitalized on an extensive forest inventory data set ( n = 615 plots across 7000 ha) to evaluate regeneration dynamics in Norway spruce Picea abies forests across the Bohemian Forest Ecosystem (spanning Germany and the Czech Republic). We asked whether neighbourhood effects (conspecific advance regeneration of spruce) would support prompt regeneration back to spruce forest, or whether the rapid, severe canopy mortality would overwhelm this influence and promote pioneer and broadleaf species. We tracked 15 years of post‐outbreak regeneration dynamics (occupancy, density, height, composition) of all tree species and evaluated initial variations in successional pathway and structure.
Median tree regeneration density increased from 400 trees ha ⁻¹ at the time of outbreak to 2000 trees ha ⁻¹ within a decade, and occupancy increased from 58% to 76%. The increases were driven by spruce, which primarily recruited from advance regeneration, gradually occupying greater height classes. Only one broadleaf/pioneer species increased in relative proportion, for a brief (<3‐year) period before declining again. Nevertheless, both pure spruce and spruce–broadleaf stands were common and, coupled with wide variations in density and height, contributed to diverse early‐successional structure.
Synthesis and applications . Contrary to common expectations, spruce beetle outbreaks in Central Europe effectively promoted their host in the long term. Outbreak‐affected forests are naturally self‐replacing even after severe canopy mortality, when positive neighbourhood effects of conspecific advance regeneration lead to rapid replacement of the dominant species. Thus, natural regeneration may be considered among the most effective ways to meet possible reforestation objectives in forests destroyed by beetles.
Background: In forests subject to stand-replacing dist